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Max-Prop Automatic Feathering Propellers

Proven Cruising and Racing Propellers Since 1972

Max-Prop has led the low drag propeller market for 40 years and is still the leader today. Since starting production in the 1970's Max-Prop has proven itself on racing and cruising boats around the world. With over 50,000 propellers in the water, the Max-Prop is tested daily in the harshest conditions and has established itself as the most efficient and reliable low drag propeller.

The combination of low drag, outstanding reverse power, efficient forward performance, and fail-safe design makes Max-Prop the ideal sailboat propeller on the market today. Now with the recent introduction of the Whisper, and the Boomerang models, Max-Prop has taken a further lead over the competition in the propulsion of sailboats.

Max-Prop Models

2, 3 and 4 Blade

For Racers to Large Cruising Boats

Easy for SailDrive

For Volvo, Yanmar, TwinDisc, ZF, Sillette or Bukh SailDrives

For Heavy Displacement Large Cruising Yachts

For Larger Vessels with Electronic Shift Transmissions and High Sailing Speeds

Features of a Max-Prop

Under sail, a Max-Prop will increase sailing speed between 10% to 15% in average wind conditions compared to a fixed blade propeller, with an ever-larger difference being given when sailing in light air. The drag under sail varies widely between propellers, number of blades, angle of the shaft as well as location of the propeller on the boat. It is fair to say that a 2 blade Max-Prop propeller located on a horizontal shaft (sail-drive) will have the least drag while a 5 blade Max-Prop on a high angle shaft will have the most drag. However, even a 5 blade Max-Prop on a high angle shaft will have substantially less drag and provide more power when motoring than a fixed 2 blade propeller.

In forward: the Max-Prop will offer 96% of the efficiency of a fixed blade propeller of the same diameter and pitch. The 4% loss in power can usually be eliminated by precisely matching the pitch of the Max-Prop to fit the boat engine combination. In reverse: the Max-Prop provides 80% more power than a comparable fixed blade propeller. The Max-Prop utilizes the same leading edge in forward as it does in reverse giving the propeller the same efficiency in both directions, whereas on a fixed blade propeller in reverse the trailing edge becomes the leading edge therefore reducing its power.

RELIABILITY

Max-Props are feathering propellers, so unlike folding propellers, Max-Props do not rely on centrifugal force to open. Instead, the Max-Prop relies on the torque from the shaft rotation acting on the differential type gear design in the body of the propeller. This in turns ensures an immediate opening in forward and more importantly in reverse, unlike folding propellers which have a lag time in reverse.

VERSATILITY

The pitch setting on all Max-Prop models can be adjusted. Changing the pitch is very simple; by removing a bolt and replacing with one of a different length on the Easy and Whisper. On the Classic models, you will need to change the setting of the gear inside the propeller (usually upon a haul out). The ability to adjust the pitch will help achieve the maximum efficiency from the engine without having to purchase a new propeller.

INSTALLATION & MAINTENANCE

The Max-Prop will fit directly onto your existing shaft with the boat in or out of the water. The Max-Prop will be matched to your specific shaft taper or SailDrive Spline. The only required maintenance is to grease the propeller once a year, and to replace anodes when they erode away.

Worldwide, many of the top racing boats have opted for the Max-Prop solution.

The three, four or five blade Max-Prop is the propeller of choice for the cruising sailor. The combination of low drag, great performance in forward, increased speed under sail, outstanding backing power, safety and maneuvering, and fail-safe design makes the Max-Prop the ideal cruising propeller.

Advantages of a Max-Prop

Under Sail...

A Max-Prop feathers to a low drag shape. Compared to a folding propeller, the extra wetted surface of the Max-Prop blades is offset by the reduction of projected area: A .

In Forward...

While not always exactly as efficient as a perfectly sized fixed propeller, a good choice of Max-Prop diameter, pitch and number of blades will usually achieve 96% or better efficiency compared to a fixed blade propeller. This maximum of 4% drop in efficiency is only seen at maximum throttle, which is seldom, if ever, used. The fact that with a Max-Prop, a boat owner or a designer can choose not only the diameter and number of blades of the propeller but can also adjust the pitch easily after sea trials makes the Max-Prop an ideal tool to fine tune a boat’s performance under power.

In Reverse...

The simple fact that the Max-Prop blades use the same leading edge and pitch in reverse as in forward results in an identical power in both directions. A fixed blade propeller looses almost 50% of its power in reverse. Worse yet - a folding propeller which, depending on the brand, can loose up to 80% of its power in reverse. The Max-Prop blades switch from forward to reverse instantaneously. It takes only 3/4 of the shaft rotation for the blade switch to occur.

"WOW! I tested it out yesterday and this new Max Prop is like night and day! It feels like I finally found the "brakes" on the boat. I should have done this years ago!! Backing up is immediate (instead of the usual almost 2 second delay), I have better control in reverse, AND so much more power going forward! Plus my boat vibrates a lot less."

Disadvantage of Folding Props

A folding propeller has low drag. The drag is directly proportional to the projected area: A .

The blades will "slam" open and, if not perfectly aligned or true to each other, will cause vibration.

In that the blades will not open to the maximum diameter (and occasionally not at all), the reverse power is very poor (much less than a fixed blade prop).

Disadvantage of Fixed Blade Props

A fixed blade propeller includes a tremendous amount of drag, reducing the boats speed an average of 15%.

Fixed blade propellers provide maximum efficiency as long as the pitch is correct.

A fixed blade propeller works with the trailing edge as a leading edge, reducing its efficiency by 50%.

Max-Prop Propellers For Catamarans

Catamarans are different from monohull sailboats under sail and power. Because of this, the advantages of the Max-Prop are accentuated on a Catamaran. The reduced drag under sail not only improves boat speed but also reduces turbulence over the rudders providing improved boat handling. This reduction in drag also allows a boat to come through a tack quicker and with more boat speed exiting the maneuver, making it easier to sail in light winds.

With the increased beam and freeboard of a catamaran comes the downside of more windage. The impressive reverse power of the Max-Prop adds to the control and safety of the vessel when maneuvering. Max-Prop has propellers for both SailDrive and Shaft driven applications in 2, 3, 4, or 5 blade designs. This allows the boat owner to pick the correct propeller for how they use their catamaran with little compromise.

Features specific to Max-Prop on Catamarans

• Improves control and safety of the vessel
• Very low drag under sail
• Reduced turbulence over rudders under sail
• Improved tacking speed with reduced drag
• Overcome windage inherent to Catamarans
• 80% more power in reverse compared to a fixed propeller
• Models designed specifically for SailDrive
• Adjustable pitch to optimize powering performance
• Versatility of blade number

Max- Prop was designed and built in the early 1970’s by Maximillian Bianchi in Milan, Italy. Max, a young Italian engineer invented a new type of propeller at the request of a sailboat racing friend in the golden days of the IOR racing rules. Little did he know at the time, this simple product would become his lifelong passion and livelihood. To this day, Max still oversees any new development of the product and follows it all the way through the manufacturing process. It is hard to believe, but Max quality checks each and every propeller that comes out of his factory. Nowadays, his son and daughter work with him so the legacy will continue long after Max retires (if he ever does).

The Foundry

In order to keep the metal quality to a constant high standard, Max bought a foundry in the mid 70's. To this day, the majority of Max-Prop cast parts are made in that foundry close to Lake Cuomo, a two hour drive from Milan.

The ownership of this foundry not only resulted in high quality cast parts, but also insured that any defect in the material or the part would not be passed on to the next stage of machining. This vertical integration is one of the main reasons for the success and durability of Max-Prop.

The Machine shop

The actual machining of the propellers has always been under the full supervision of Max, from the days of manual lathes and mills to the ultra-modern CNC machines of today. Through the years, the machine shop has had multiple locations and currently is in Milan, in the same building as the sales offices, management and where the final assembly of the Max-Prop occurs. Once again, Max himself oversees each and every process.

Sales Office

PYI is the only sales office for Max-Prop in North/South America and Asia. PYI was established in 1981 and on that date Max-Prop was already the main product distributed. Since then, PYI has added products which are well known in the sailing community, some as a manufacturer and some as a distributor. Through the years, Max-Prop has been the driving force for PYI, allowing us to facilitate the manufacturing of other quality products.

Max-Prop Through The Years

An evolution towards perfection!

Maximilian Bianchi Circa 1972

Maximilian Bianchi Circa 2018

Max-Prop Videos

Want to learn more about our Max-Prop products or how to adjust or install a Max-Prop? Check out our Youtube channel for all of our videos.

Other Max-Prop Videos

• How to assemble a 3 blade Max-Prop Classic
• How to assemble a 2 blade Max-Prop Classic
• How to disassemble, determine pitch & rotation of a 3 blade Max-Prop Classic
• How to disassemble, determine pitch & rotation of a 2 blade Max-Prop Classic
• How to install a Max-Prop Easy & Whisper
• How to adjust pitch &rotation of Max-Prop Easy & Whisper

Download our Max-Prop catalogs, installation instructions, price lists right here. Can't find what you're looking for? Contact us and we'll help you out!

Catalogs & Price Lists

• Max-Prop Catalog
• Max-Prop Price List

Max-Prop Installation Instructions

• Max-Prop Classic 2 Blade Installation Instructions
• Max-Prop Classic 3 Blade Installation Instructions
• Max-Prop 3 Blade Classic Removal Instructions
• Max-Prop Easy & Whisper Installation Instructions
• Max-Prop VP Installation Instructions
• Max-Prop 3 Blade Gen II Pitch Adjustment Instructions
• Max-Prop Classic Gen II Installation Instructions
• Max-Prop Ecowind Installation Instructions
• Max-Prop 3 & 4 Blade Fast Insatllation Instructions
• Max-Prop Zerc Installation Instructions
• Max-Prop Recommendation Sheet
• Max-Prop Service & Repair Form
• Zinc Identification Sheet

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Choosing the Proper Sailboat Prop

• By David Schmidt
• Updated: July 21, 2021

As sailors, it’s romantic to think that our locomotion comes from the wind, but most skippers, when pressed, admit to motoring a fair portion of the time. Like it or not, your boat’s propeller is a key element of the propulsion system, and just as there are myriad considerations involved when ordering sails, decisions abound when selecting the prop that best suits your wallet and sailing plans.

Fixed-Blade Options

As the moniker implies, fixed-blade propellers are typically cast out of an alloy such as manganese bronze or nickel, bronze and aluminum. Individual propeller blades stem from a central hub, which in turn attaches to the sailboat’s prop shaft or saildrive. Depending on the manufacturer, these blades typically are pitched in a way that propels the boat forward or backward when the transmission is engaged. The term “pitch” refers to how far forward or reverse a propeller will theoretically travel through a solid material (picture a screw twisting into a wood block). For example, a prop with a 12-inch pitch will theoretically move through 1 foot of solid material with each full rotation.

Sailors have choices available when buying a fixed-blade propeller, with the biggest variables being the ­diameter, the number of propeller blades, and the pitch. Just as sailboats create “dirty air” that spills off their sails, propeller blades push water against the hull, which then reverberates back (call this “dirty water”). When the transmission is in forward, this dirty water is sent back toward the rudder, which can influence steering. An important rule of thumb for all propeller designs and types is to ensure that the propeller has a tip clearance (the amount of space between a blade’s tip and the hull when the blade is in the 12 o’clock position) that’s at least 10 percent of the length of the prop blade (hub to tip). If you don’t have enough tip clearance, the next step is to spec a smaller-diameter propeller with an extra blade. Fixed props are available with two, three or four blades.

While this can be an easy fix, additional blades create additional drag when the boat is sailing. Because of this, sailors who opt for a fixed-blade prop are typically best served choosing a screw with the fewest number of blades that can properly fit their boat and their engine (see “Choosing Screws,” right). That said, additional blades equate to more power when motoring into a stiff headwind, current or big seas. Additional propeller blades can also accommodate a more powerful engine at a given diameter. These latter points are important if you’re planning on cruising unfamiliar waters and might find yourself negotiating a lee shore under power.

While fixed-blade ­propellers are strong, simple, relatively inexpensive, and ­easier to have repaired in remote locales, they do affect sailing performance. Moreover, they’re more likely to foul a lobster pot or other fishing gear than a folding prop when the boat is sailing. If you care about sailing performance, especially in the light stuff, or if you’re planning a long-distance cruise, purchasing a folding or feathering prop is a wise investment. But if you’re seeking maximum power or punch for your buck, and you sail on breezy waters such as San Francisco Bay, where extra drag isn’t a huge concern, a fixed-blade prop could be the way to go.

Folding Propellers

Folding propellers employ a series of gears (situated around the prop’s central hub and on the inboard end of each prop blade) and centrifugal force to open when the engine’s transmission is engaged. The slipstream action of the passing water acts to fold them closed when sailing, and their gear mechanisms hold the blades in their closed position even in light airs. As with fixed-blade props, sailors can choose between models that feature two, three or four blades. Unlike fixed-blade props, however, folding propellers create far less drag when the boat is sailing.

“For the same diameter and number of blades, folding propellers have 85 to 100 percent less drag than a fixed prop, depending on the fixed propeller’s blade area and the folding propeller’s make and model,” says Geoff Prior, owner of AB Marine, the Newport, Rhode Island-based importer and distributor for Gori folding props and AutoProp, Variprofile, and Variprop feathering propellers. “Geared folding propellers stay closed or folded when the boat is sailing, so a blade cannot drop down to be exposed to the water flow, and does not catch lines and weeds like fixed and feathering propellers can.”

Others agree. “Most sailboats will gain 0.5 to even 1 knot of speed by using a low-drag folding propeller,” says Keld Willberg, Flexofold’s general manager. “Many boat owners don’t look just at the speed gains, but also the ability to sail in very light wind.” Also, he says, when tacking, a boat that’s equipped with a low-drag prop won’t lose as much momentum.

This latter point is critical to anyone who sails in places with typically light breeze. “The folding propeller’s drag reduction and increased sailing speeds produce less turbulence over the rudder, enabling you to point higher, steer easier and more precisely, and tack and jibe the boat easier,” Prior says. “The biggest speed difference is in light or medium air and with clean water flow over the rudder—the boat is a lot more responsive, especially when fine sailing on the wind.”

One important consideration when selecting a folding prop is ensuring that your boat can physically accommodate the length of the prop when it’s folded. This is especially important on full-keel boats that have an aperture between the keel and rudder. For anyone who cruises with a saildrive(s), Prior advises that saildrive propellers must be approved for use by the saildrive’s manufacturer to ensure that the prop is electrically isolated from the saildrive’s leg and shaft; also the prop’s hub must incorporate a rubberized bushing to absorb shock and inertia, as well as an easily changed and ­streamlined anode.

As with all props, ­selecting the diameter, number of blades, and pitch of the propeller are all key decisions. “Diameter is the single most critical factor in determining the amount of power that a propeller absorbs and transmits into the water,” Prior says. “It’s the most important single factor in determining the amount of thrust delivered. The larger the diameter, the greater the efficiency. A small increase in diameter dramatically increases thrust and torque load on the engine and shaft.”

Blade count is also critical, but Willberg cautions that it’s overly simplistic to think that additional blades equate to additional power (see “Calling the Pitch,” right). “What ­matters is to get the right combination of blade area and pitch for the engine and gear box,” he says. “On flat water, a two-blade propeller can be just as efficient or even slightly better than a three-blade. However, when motoring against wind and waves, and when maneuvering, you get more power from a ­three-blade prop.”

Blade shape also matters. “Propellers with flat, planar blades are like a paddle,” Prior says. “The flat shape is not ­efficient at producing thrust because a flat blade is overloaded at the tip and underloaded at the blade base, whereas a fully shaped airfoil blade shape has a constant loading over its whole surface.” Much like fixed-blade props, most folding propellers employ an efficient blade shape, while feathering props use flatter and more ­planar-shaped blades.

One drawback of most (but not all) folding props emerges when the transmission is put into reverse. “In reverse, the suction side is on the back or aft side of a blade, and with the typical folding propeller design, the blades are trying to close in reverse, giving low thrust and lots of prop walk,” says Prior, who added that Gori’s three-blade prop presents identical leading-blade edges in both forward and reverse, negating this issue. Willberg advises that folding props require slightly different operation than fixed-blade or feathering props to ensure that they stay open. “For more stopping and reverse power, it’s just a matter of giving more revs on the throttle,” he says.

RELATED: Understanding Your Sailboat Propellers

As with all props, folding propellers must be kept clean of marine growth, and anodes must be regularly changed to ensure cathodic protection. “One millimeter of growth on a blade and your propeller loses approximately 12 percent efficiency,” Prior says, adding that this applies to any make, model or design. And, he notes, “folding propellers are water-lubricated, so they do not need to be greased.”

The final consideration is cost. Folding props are roughly four to six times more expensive than a fixed-blade propeller for a given diameter and blade count. While this is a big difference, the gains are huge, and—for bluewater cruisers—can translate to ­significantly faster passage times (potentially measured in days) and happier crews.

Feathering Propellers

As do folding propellers, feathering props greatly reduce drag when the boat is sailing; however, the way that they achieve this gain is significantly different. Moreover, the physics behind how the prop transitions from its sailing mode to motoring mode is also different.

Feathering props are available with two-, three-, four- and five-blade configurations. A central hub attaches to the prop shaft or a saildrive, and it features a series of internal beveled gears. Geared propeller blades attach to the hub and rotate through 180 degrees, depending on if the transmission is in forward or reverse (more on this later); this articulation is governed by machined stops inside the hub that prevent the blades from overrotating. When the transmission is engaged, the blades present their broad sides to the slipstream, but when the boat is under sail, the blades rotate 90 degrees to align with the flow of the water.

“Feathering props work off torque from the shaft or saildrive,” says Fred Hutchison, at PYI, which distributes Max-Prop feathering propellers. Because feathering props use torque—not centrifugal force—to open, it’s “instantaneous,” says Hutchison, who points to this as the design’s biggest advantage. “It takes a feathering prop only three-quarters of a turn to go from full forward to full reverse. In that time, the blades rotate 180 degrees, and it doesn’t generate much shock load.”

Prior adds, “In the sailing position, the water flow turns the blades to the feathered position when the engine is off for vastly reduced drag.” He estimates that this drag reduction is approximately 85 percent compared with fixed-blade props.

As previously mentioned, feathering-prop blades rotate through 180 degrees, which is a big advantage when operating in reverse compared with most folding props. “A feathering propeller gives reverse thrust with the same efficiency as in forward, as the leading blade edge in forward is turned 180 degrees, and without prop walk,” Prior says.

Another advantage of feathering props for boats with full keels or with tightly spaced skegs or rudders is that they “can fit in a small aperture as they have shorter overall lengths compared to folding propellers, which have a greater length when folded,” Prior says. “If there is a diameter constraint, the feathering prop can easily be designed and built with a higher pitch to make up for the loss of diameter and blade area.”

Most feathering props are machined out of a nickel, bronze and aluminum alloy, which, Hutchison says, makes them easy to repair. Unlike fixed or folding ­propellers, feathering propellers employ flat-shaped blades to reduce drag when the boat is sailing. “Feathering propeller blades are foiled and aren’t as efficient as the helical twist found on most fixed-blade or folding props,” Hutchison says, adding that manufacturers compensate for this less-efficient shape by increasing each blade’s surface area. “Blade surface area and shape make a big difference in how efficient it is,” he says. “No low-drag prop will be as efficient under power as a fixed-blade propeller.”

Lobster pots and fishing nets are common concerns when operating under auxiliary power, and feathering props are not snag-proof. “When motoring, feathering props are the same as fixed-blade and folding propellers,” Hutchison advises. “But when sailing, a folding propeller has less of a chance of catching a pot or fishing net than a fixed-blade or feathering propeller.” This is a consideration for anyone who cruises extensively in, say, Maine or in heavily fished waters off the West Coast.

As with all propellers, feathering props require basic care and maintenance to ensure their efficiency and the engine’s longevity. This starts with a properly spec’d and regularly refreshed anode, and the prop blades must be kept clean.

Unlike folding props, which typically use exposed self-­lubricating gears, the internal gears of feathering propellers need to be greased annually. While this adds an item to an owner’s yearly to-do list, Hutchison says that this can be tackled by a diver.

Finally, while feathering props are a great upgrade, they don’t come cheap. “Feathering props are more expensive than folding props,” says Hutchison, who ­advises that a feathering prop is roughly 10 to 15 percent more ­expensive than a folding prop with the same blade count and a ­comparable diameter. “This is primarily because of ­machining costs,” he says.

David Schmidt is CW ’s electronics editor and also writes about topics ranging from sailing gear to environmental issues from his home in Bellingham, Washington.

Choosing Screws

Choosing the right propeller is complex, but the most important variables for selecting the correct prop are your boat’s make, model, LOA and displacement, the engine’s horsepower rating and its maximum rpm, as well as the transmission’s reduction ratio. While most of this information is easily ascertained, determining the reduction ratio can be challenging. But, Prior says, “the best method to get the actual ratio is to use your cellphone camera and take a photo of the plate on the transmission,” adding that this beats hanging upside down and trying to read this information using a mirror and flashlight. For the DIYer, online calculators exist that can help crunch the numbers. “After that, it gets into the art,” Hutchison says. His advice: Ask an expert.

Calling the Pitch

Unlike fixed-blade propellers, feathering and folding propellers are often designed so that the pitch can be adjusted, perchance it doesn’t perfectly match your vessel, engine and transmission right out of the box. Depending on the prop, this adjustment is typically made by changing a screw(s) or swapping out the prop blades. These adjustments can usually be done by a diver while the boat is in the water. Some general rules of thumb as to when to change the pitch involve engine rpm: If the prop doesn’t meet the engine’s ideal rpm, the blade’s angle needs to be reduced; conversely, if the prop is exceeding the engine’s rpm metrics, the blade’s angle of attack needs to be increased. As a cautionary note, overpitching a propeller can cause the engine to overheat, and it can also lead to injector-choking problems and create excessive internal engine pressure, so be sure to stay within the engine ­manufacturer’s lines.

Vendor Information

EWOL: ewoltech.com , 410-317-8104; from $2,120

Flexofold: flexofold.com , 781-797-0809; from $980

GORI: gori-propeller.com , 401-847-7960; from $650

J Prop: betamarinenc.com , 252-249-2473; from $2,500

Kiwiprop: kiwiprops.co.nz , 877-549-4872; from $1,350

Max-Prop: pyiinc.com , 425-355-3669; from $1,900

Michigan Wheel: ­ miwheel.com , 800-369-4335; from $550

Variprofile: spw-gmbh.de , 401-847-7960; from $800

Variprop: spw-gmbh.de , 401-847-7960; from $1,200

Volvo: volvopenta.us , 800-522-1959; call for pricing

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Feathering Marine Propellers                                         

Feathering propellers provide a host of advantages over folding and fixed blade propellers for sailing vessels, whether cruising or racing. Conceived and designed specifically for sailors, feathering propellers increase sailing speeds by reducing drag, they improve boat maneuverability (i.e. eliminating prop walk) and they reduce wear on drivetrain components. Our feathering propellers are easy to install, easy to adjust pitch, and built tough with premium materials to handle the rigors of ocean life.

We are proud to offer two superior lines of feathering propellers. EWOL and J-Props are two of the best products in the industry. Call us to discuss our propeller options that are suitable for your vessel.

Why a Feathering Propeller?

• Increase Sailing Speeds –  Up to 1.5 knots more under sail
• Greater Performance Under Power – Micrometric pitch settings allow you to optimize cruising speed
• Improved Handling – Improved Backwards Thrust Virtually Eliminates “Prop Walk”
• Easy Installation, Maintenance and Removal

EWOL & J-Prop Advantages

• Easy Adjustment – No tools needed! Simply pull and turn hub to adjust pitch. No costly haul out necessary.
• Precision machining. Use of helical gears ensures reduced wear and enhanced durability.
• High quality materials. Super tough aluminum-bronze alloy and stainless steel construction offer enhanced corrosion protection and durability from prop strikes.
• Low maintenance. Simply add grease annually (can even be done in the water).

J-Prop 2 Blade Feathering Propeller

J-prop 3 blade feathering propeller.

EWOL ANDROMEDA – 3 Blade Feathering Propeller (13”-17”)

EWOL ORION – 3 Blade Feathering Propeller (19”-24”)

Ewol orion – 3 blade feathering propeller for saildrives (15”-18”).

J-Prop 4 Blade Feathering Propeller

J-Prop EP Feathering Propeller

J-Prop Saildrive Feathering Propeller

Yachting Monthly

• Digital edition

How to choose the right boat propeller

• Sam Fortescue
• June 20, 2024

A change of boat propeller can dramatically improve a yacht’s performance while saving money on fuel. Sam Fortescue reports on the latest options

A well-known truism of boat ownership is that sailing with a fixed propeller is akin to towing a bucket astern. We all know that a feathering or folding propeller has huge advantages under sail, but what are the costs of motoring with a sub-optimal propeller? Even purists will use the engine to manoeuvre in and out of busy harbours, and most of us are willing to fill in with horsepower when the wind drops.

You won’t be surprised to hear that propeller manufacturers believe that sailors often have the wrong screw fitted. And if that delicate balance between the propeller size, engine power and the boat’s speed potential don’t align, you’ll be losing money to inefficient performance under power.

‘It’s pretty common that props aren’t the right size,’ explains David Sheppard, managing director of Bruntons, maker of the Autoprop. ‘The usual first sign is that the engine is being overloaded or underloaded. If it doesn’t reach its full rpm, then it’s overloaded. And if it’s underpropped, you’ll get revs above the rated rpm. It’s more difficult to tell with modern diesels, but in the old days, you’d get black smoke coming out of the back because there’d be too much diesel going in and the engine wouldn’t be able to turn fast enough to burn it.’

There are some reasons why you might want to be overpropped, but engine manufacturers will often void the warranty if the propeller is incorrectly sized. Worse still, you’ll be putting additional wear and tear on the engine which will result in a shorter service life and greater maintenance. With labour rates of £50-80/hr, even minor repairs can cost hundreds of pounds, with any new parts taking it into the thousands.

Check that you have a viable engine-to-prop gear ratio. Note that additional blades can be used where there isn’t sufficient space for a larger diameter prop, as on this four-bladed Maxprop. Photo: Jack Patton

Prop mismatch

A mismatch between engine and prop often creeps in when a boat is repowered. ‘We usually get customers ringing up after their boat’s been re-engined,’ explains Chris Hares of Darglow Engineering, which manufactures the FeatherStream propeller. ‘If you just take out an old 30hp engine and replace it, you can end up with a different gear ratio that requires a different propeller.’

For many cruising boats with faster turning engines, a 2.6:1 gear ratio gives the best balance between prop diameter and speed. A low 2:1 ratio means a higher propeller speed and therefore a smaller diameter. The opposite is also true. There is a lively trade in 10-year-old Bukh DV20/24 lifeboat engines, which have to be replaced by law but have seen little use. They use a high 3:1 reduction ratio which requires a bigger-than-average propeller, and most sailing boats simply don’t have the space for it.

‘People can spend £9,000 repowering the boat and then find it performs worse than it did beforehand because it’s got a higher shaft speed and isn’t efficient,’ says Hares.

And don’t think that new boats are immune to this problem, either. When Yanmar replaced its popular 3YM30 with the 3YM30AE, it took time for some boatbuilders to notice the max revs had been cut from 3,600 to 3,200.

‘Designers usually know what they’re doing, but what goes wrong is when the supply of engines or gearboxes changes and nobody connects the dots,’ Hares says. ‘We saw it a lot during Covid because of the supply problems.’ Ideally, you want the engine to hit its rated rpm with the throttle fully open, and it is simple enough to test. ‘You need to take the boat out on a fine day before it gets covered in barnacles and going full throttle,’ says Hares.

An Autoprop consumes a third less diesel than a fixed propeller

Money savings

If you’ve established that your engine and propeller combination isn’t giving you the performance it should, or if you’ve decided it’s time to invest in a feathering or folding prop to increase your sailing speeds and reduce passage times, what next? Well, working out a budget is a good first step.

Feathering props are on average 20 per cent more expensive than folders, if you overlook the good-value Kiwiprop. This alone might be enough to steer you one way or another.

Set against this is the efficiency of the propeller itself under power. Trials by French sailing magazine Voiles offer a good insight. In tests with a 34ft Jeanneau using a 29hp Volvo engine with a top rpm of 3,600, the Autoprop, Gori and Flexfold all outperformed a fixed prop.

The Autoprop consumes a full one-third of a litre less diesel per hour to maintain six knots of boat speed – a saving of around 50p/hour at current pump prices. The difference between the Autoprop and the worst performing feathering propeller was starker still – nearly one litre per hour.

But perhaps more striking than the potential fuel savings is the gain in range. At six knots, the Autoprop could manage 42.5 miles on 10 litres of diesel. The fixed prop gave 34.6 miles and the Maxprop managed just 27.2 miles.

The test was done in flat water conditions, but it illustrates the big differences in safety cushion offered by the different prop designs.

The most efficient pitch-to-diameter ratio is 2:3

What size boat propeller do you need?

Sailing boats should have large propellers, turning slowly with minimal slippage. However, there is limited space under the hull, so the smallest blade and least amount of drag, is best.

‘The most efficient pitch-to-diameter ratio is 2:3,’ explains Hare. ‘But it’s not always possible to do that because there isn’t always enough room to accommodate that diameter.’

Pitch is the distance the prop would travel forwards in a rotation through a soft solid. Thus, a 15in pitch means that the propeller blades are angled so they would advance 15in in a single rotation if there were no slip.

‘There’s an optimum diameter and pitch,’ adds Sheppard of Bruntons. ‘If you can’t fit that, you get a restricted-diameter prop, with greater pitch. The more you compensate, the less efficient the prop becomes. You don’t always notice it on a heavy sailboat, but it’s important because you get more prop walk due to the greater paddlewheel effect.’

Space below the hull limited prop diameter on this boat hence the five-bladed Maxprop, at the cost of additional drag

How many blades?

For engines below 100hp, you don’t need more than three blades. On saildrive yachts with plenty of hull clearance, it’s common to have a larger two-blader, which is efficient but subject to vibration. It’s essentially a case of having sufficient blade area to handle the horsepower. More blades means more drag, but when there isn’t space to fit the right size prop you might need an extra blade.

The Featherstream hybrid propeller with stainless steel blades and a bronze body

What’s the best material for a boat propeller?

We tend to think propellers should be made from honey-coloured bronze, but they are, in fact, usually made of a complex alloy involving copper and tin plus differing amounts of aluminium, nickel, manganese, zinc and iron, which results in a material with good corrosion resistance that’s easily machined.

Italian firm Ewol, however, builds beautiful, but expensive, feathering props from polished stainless-steel because it is less susceptible to galvanic corrosion from stray current while offering greater strength for a finer profile.

Seahawk, meanwhile, has less expensive stainless props with its Autostream and Slipstream cast in 316 and 2507 steel, while Darglow has developed a bronze body with stainless steel blades in a hybrid called the Featherstream.

Polished stainless-steel prop from Ewol. Note the bronze bushings to prevent steel-on-steel wear

‘All-bronze props will wear out quicker and need reconditioning sooner on the blade bearing surface, where it rubs against the hub,’ explains Hares. ‘But, it’s very difficult to have an all-stainless prop. You can’t run stainless steel on another piece of stainless as a bearing surface, where they catch each other and get stuck. So, you need a bronze bushing between blade and body, which tends to wear down quite fast.’

Composite propellers are a cheaper solution to the corrosion problem, with the best-known being the Kiwiprop, whose black Zytel blades are mounted on a stainless steel pin and never wear. They’re not the most efficient blades, due to their broad, flat profile, but they are the cheapest feathering option.

Flexofold also produces a folding two- and three-blade prop with a composite boss, which provides the same galvanic isolation.

Gori’s folding propeller can swivel to offer the leading edge in reverse

Folding vs feathering boat propellers

Compared with a fixed propeller, either option will offer massive improvements in hydrodynamic efficiency under sail. You can expect 10-20 per cent more boat speed in given wind conditions – at least half a knot and possibly more than one knot for bigger boats, enough to save an hour sailing a 40ft yacht from Dartmouth to Plymouth.

It’s harder to draw a distinction between the drag from a feathering propeller, such as the Autoprop or the Kiwiprop, and a folding prop.

‘Feathers have flat blades which reduces their efficiency a little, to perhaps 95% of a folding prop,’ says Hares at Darglow. ‘But most sailing boats have more than enough power in the engine, so you’re going to hit hull speed with any of these, but you’ll burn less fuel with a folding prop.’

The Flexofold feathering prop is having success with electric motors

Of more concern are the other variables around prop design, such as maintenance, performance astern, regeneration potential and noise/vibration. Folding props tend to be easier to maintain with fewer wearing parts and no annual greasing. They may also be more efficient motoring ahead. A feathering prop, meanwhile, will go much better astern.

With the exception of the Gori, folding props can’t swivel to offer the leading edge in reverse, which makes them just as inefficient as a fixed prop. Their design also means that the thrust they generate astern is trying to close the propeller, so, you need to give the engine higher revs, and that means more prop walk.

‘If you’re struggling with a fixed prop, that’s going to get worse with a folding prop. Feathering props are much better at stopping the boat and give less prop walk than folders as you can manoeuvre with a modest amount of throttle.”

SPW’s new Variprop GP has been specifically designed to offer efficient regeneration

Boat propellers for electric

There is no real difference between the dimensions of a prop for electric vs diesel operation if all other variables remain the same. However, the high torque often means electric systems have lower shaft speeds, which will require a bigger prop or an extra blade to increase power transmission.

‘If you’re putting in an electric motor, we specify a very slow shaft speed and a slow-turning prop because the torque is flat, which is good for a propeller,’ says Sheppard. ‘Otherwise, considerations are broadly the same.’ But because regeneration is so important in an electrical system, feathering props dominate. The hybrid folding-feathering Gori can regenerate, and Flexofold reports some success too, while the Kiwiprop and Seahawk’s Autostream are not suited.

Of the feathers, Bruntons has re-engineered its Autoprop specifically to increase regeneration potential. Called the Eco Star, it can produce 200W at five knots of sailing speed or 550W at seven knots. Ewol has also developed an expensive regen version of its three-bladed Orion called the EnergyMatic, and SPW’s new Variprop GP has been fine tuned for regeneration.

Oceanvolt’s award-winning HighPower ServoProp 25

Variable pitch boat propellers

Variable pitch propellers are commonly found on large ships, but Oceanvolt has developed a small-scale product for the cruising market as part of its electric propulsion package. Its ServoProp is a unique feathering three-blader for saildrives, which can rotate more than 180 degrees to present the leading edge both forward and astern. But its clever electronics are all directed at a single purpose: generating power. Paired with an Oceanvolt electric motor, the ServoProp can be used to make electricity when the boat is under sail.

It adopts an optimal pitch for being dragged through the water to produce around three times as much power as a fixed-pitch propeller. The latest HighPower ServoProp 25, launched this year, has continuous pitch control for even better regeneration and more efficient motor sailing. Ideal if you’re looking to fill a big battery bank and give yourself near endless range.

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Reduce Drag When Sailing With A Folding Or Feathering Propeller

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Learn how this time-tested piece of running gear can give your boat a power boost under sail.

Photo: Stacey Nedrow-Wigmore

One thorny debate among sailors is whether it's better to let a propeller freewheel (rotate while sailing) or to lock the shaft and hold the prop steady. Whichever camp you fall into, there's no denying that a fixed prop creates drag that slows down your boat.

Consider this: If your boat has a fixed three-blade prop, you could be losing as much as a knot of speed when sailing (as verified in an independent test of several props by the author aboard his own 33-foot sloop). In other words, if your boat typically cruises around 5 knots, switching to a folding or feathering propeller could ramp up that speed to 6 knots — that's a 20% increase! Over a typical 30-mile voyage, that translates to arriving one hour sooner.

Folding and feathering props are nothing new and have been around in one form or another for more than half a century. Early props had just two blades that relied solely on centrifugal force to open them. While these props work well enough for many sailors, they have a few shortcomings: They don't work too well when maneuvering around the docks, especially when backing. And should one blade open slightly more than the other, excessive vibration can occur, causing wear to the shaft log and cutless bearing.

Newer types of folding props, such as the Flexofold , may have two or more blades interconnected to each other with a gear mechanism. This ensures that when the shaft starts rotating, they open symmetrically. Other brands include Gori Prop , Varifold , and Slipstream .

However, folding props may not work for some boats, especially if the rudder is close to the propeller hub preventing the propeller from completely folding. In this instance, a feathering prop, such as the Max-Prop , may be a better choice. Other brands include Kiwiprop and Variprop . With a feathering prop, the blades are symmetrical and rotate around a central pivot point and offer as much thrust in reverse as they do in forward gear — a boon for getting into a tight slip. When sailing, the blades align themselves with the flow of water, reducing drag.

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Contributing Editor, BoatUS Magazine

A marine surveyor and holder of RYA Yachtmaster Ocean certification, BoatUS Magazine contributing editor Mark Corke is one of our DIY gurus, creating easy-to-follow how-to articles and videos. Mark has built five boats himself (both power and sail), has been an experienced editor at several top boating magazines (including former associate editor of BoatUS Magazine), worked for the BBC, written four DIY books, skippered two round-the-world yachts, and holds the Guinness World Record for the fastest there-and-back crossing of the English Channel — in a kayak! He and his wife have a Grand Banks 32.

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Ewol feathering propellers make maneuvering easier, increase sailing speed and increase cruising speed under power

EWOL adjustable pitch propellers are made of stainless steel alloys that represent the highest technology in terms of marine corrosion and galvanic corrosion resistance, and are also equipped with the most refined technical solutions that make it unparalleled on the market.

EWOL feathering propellers can be fitted on sailing boats with both traditional (endothermic) and electric engines and with both mechanical and hydraulic inverters. The components of EWOL propellers are made of super-duplex stainless steel alloys, developed by the steel industry for extremely heavy tasks.

EWOL regularly presents new versions of its products with increased performance, and is now also working on developing additional innovative products that will come out in the short and medium term. Nowadays, anyone seeking a truly reliable product that performs over time, solves boat manoeuvrability and sailing speed problems, and is always up at the cutting edge of technology and materials, should install an EWOL propeller on their boat.

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• Systems & Propulsion

Folding vs. Feathering Props

With a new engine, mahina tiare gets a new streamlined screw..

For the past 40 years we’ve sailed an average of 10,000 miles annually between Australia, Alaska, Antarctica and Spitsbergen motoring or motorsailing between 400 and 600 hours, depending on the area – more hours in high latitudes of Antarctica and the Arctic, fewer in the tropical trade winds.

Our HR 42 came with a fixed three-blade prop which served us well when pushing bergy bits out of the way in Patagonia, Antarctica and Alaska, but obviously slowed us down in light airs. When we had our current Hallberg-Rassy 46 built in 1996, anticipating better sailing performance, we opted to install a Max-Prop as that was acknowledged as the best option at that time.

Max-Prop has been around since the early 70s and is a proven design, but after 18 years and 190,000 miles of use, we had the prop rebuilt three times, each time costing between $800 and $1,200. The first time the prop was rebuilt by Henleys, an Auckland prop shop, and the other two times by PYI, the U.S. importer/distributor located near Seattle. I was told that the rebuild included brazing more bronze on to the props inside working surfaces followed by machining the built-up surfaces down to original tolerances. When I enquired what I could do to extend the period of time between rebuilds, PYI said, More grease! So for 15 years, we not only greased the prop before launching at the start of our season, but also mid-season going underwater with mask, fins and grease gun to do so.

The advantages of the Max-Prop are very little drag when sailing as the prop instantly feathers unless the engine is engaged, no freewheeling in neutral, adjustable pitch, and incredible stopping power in reverse. Max-Prop can literally bring a boat from 6 knots to a dead stop in a boat length. This feature has kept us from nailing coral heads at least twice. The ability to adjust the pitch to maximum engine efficiency improves fuel economy and the newer Easy model Max-Props can be adjusted in the water without having to disassemble and reassemble the propeller, which is a substantial improvement over the earlier Classic version. We did encounter (and frequently use to our advantage) fairly substantial propwalk.

The disadvantages are that when the Max-Props feathers, the blades are still open and prone to fouling lines and kelp. During our 2008 Atlantic crossing we had to get in the water with mask and fins three times to remove cargo nets and large 3-inch floating lines from the prop. The Atlantic Ocean has a garbage gyre similar to, but smaller than the Pacific Garbage Patch, and we must have found the edge of it during our 2008 crossing. Last month, we completed the identical route from the Canary Islands to Antigua with only one sighting of trash and favorable winds that allowed us to basically sail the rhumbline. As a funny side note we were once making landfall at Fastnet Rock when a smaller boat passed us under sail. Trim as we might, we couldn’t catch them and only when they were several boat lengths ahead did Amanda think to check astern only to discover a fat turquoise rope trailing behind. The rope, obviously was not ours, was caught on the prop and we wondered how long it had been there as we’d not used the motor for several days.

During a 2015-2016 winter refit in Sweden, after reading the results of two European propeller efficiency tests and after speaking with several owners who had switched from Max-Prop to Flexofold, I had a Flexofold prop installed. Jack Skrydstrup, Flexofolds Danish manufacturer recommended the size and pitch, and the boatyard installed it without problems.

In comparison the stopping power is not nearly as good as with the Max-Prop, and the prop freewheels when the engine is shut down in neutral. Weve found that shutting down in slow forward solves the freewheeling issue. Strong on the Flexofolds plus side are blades that feather aft, instead of extended, so they’re less likely to snag lines or kelp. We notice almost no propwalk in reverse. In addition, cost of ownership is reduced as there doesn’t appear to be a need to rebuild and there are considerably fewer spare parts to carry.

However, the improvements in efficiency are difficult to quantify as we also repowered at the same time, switching from a 95 hp. to 75 hp. engine, but our top speed rose 0.7 knots, and fuel consumption on an identical Atlantic crossing dropped from 1.33 gph to .83 gph.

On the service side, PYI, the U.S. importer/distributor of Max-Prop is renowned for their customer service, doing a superb job of shipping spare parts immediately and quickly handling rebuilds from their shop near Seattle. Flexofolds Jack Skrydstrup is helpful, and ships quickly, although shipping is factory-direct from Denmark. Ive only heard one incident of an owner needing parts during European summer vacation period when shipping was delayed slightly.

Amanda and John Neal spend seven months at sea sailing 10,000 miles a year while leading sailing training expeditions. The have more than 500,000 sea miles combined experience.

Nigel Calder, author of The Boatowners Mechanical and Electrical Manual shared propeller data collected during the course of his recent hybrid propulsion experiments. Here’s his summary: “We tested Flexofold, three Goris, two Volvo-Penta four–blade folding props, three Brunton Autoprops, a Brunton Varifold, and a fixed pitch, which was undersized so not a fair comparison – it just happened to be available. The objective of these tests was to collect baseline data for other purposes. As such, the propellers were not necessarily properly matched to the boat and these are not apples-to-apples comparisons. “The Flexofold, Volvo-Pentas and Varifold had similar efficiencies, but from an engineering perspective the Flexofold was the simplest design and easiest to fit.”

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Our experience with Flexofold is that they have not stood behind their size / pitch recommendation. Great prop otherwise — well made and much more efficient than our Max Prop.

I am considering installing a Brunton Autoprop on my 34’ Vashon cutter (26’ LOD), 6500# displacement. Has anyone had experience with these props and/or what is your opinion of installing this type of feathering prop?

It would be helpful if you labeled the pictures so that us less knowledgeable sailors knew what prop we were looking at. Very good overview article considering all of the variables involved. It provided some insight. By way of an example, I tried 3 different props on my dingy before I found the best fit for my needs; a boat is more complicated.

I absolutely love the concept of the Autoprop. After having held one at a boat show, and seeing a cutaway model, I still can’t figure out how it works, but that doesn’t stop it from being brilliant. Alas, when we re-propped our Marshall 22 catboat, there wasn’t enough room for any of the Autoprop line.

We chose a 12″ three-bladed Featherstream and are very happy with it. On the downside, you have to remove a pitch “cassette” (a specifically-sized arc of metal) and replace it with a different size in order to change the pitch. But on the upside, man is that simple. You don’t even have to fully-disassemble the prop to do it. A fellow at the boatyard watched wistfully as he talked about having to disassemble is feathering prop and try to figure out which detent a screw would fit into when covered with grease.

The price was also quite reasonable, and service from Canada has been great.

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Folding Propellers vs. Feathering Propellers

Unlike a fixed propeller, which is known for creating a substantial amount of drag when sailing, fitting a folding propeller or feathering propeller will increase your speed under sail while significantly improving marina handling.

One of the most debatable and divisive issues in sailing is the varying schools of thought as far as the best sailing propeller is concerned.

Whether you believe in using the motor as your main propulsion or you fall in the purists' category who believe that a propeller should only be used for getting in and out of a marina, one thing is for sure: propeller drag is and has always been a major issue for sailboats since the invention of propellers.

While fixed three-blade props are essential in providing superb motoring performance, they can negatively affect your speed and performance when under sail. To avoid this, you should consider choosing between folding propellers and feathering propellers.

Fixed propellers are known to cause significant drag that can negatively affect your sailing speed and performance when under sail. This means that we're only left with two options: folding propellers vs. feathering propellers.

The debate generally revolves around whether you should let the propeller rotate while sailing or put a stop to the spin

Studies have proven that folding and feathering props can create less drag and in turn enhance your boat's speed and performance, especially when compared to fixed props.

But even after discarding fixed props for the considerable amount of drag that they cause, we still have to choose between folding propellers and feathering propellers.

This is what this article is all about: folding propellers vs. feathering propellers. At the end of this read, you should be able to differentiate the two and choose the right one for your sailing escapades.

Table of contents

The Importance of Choosing the Right Propeller for Your Sailboat

Your sailboat's propeller plays an integral role in enhancing its speed and performance. Whether you're planning to make a long-distance passage or trying to outrun an approaching storm, you probably have realized that an extra knot makes a whole lot of difference. An extra knot can not only save you time but also be the difference between life and death, so it should never be taken for granted.

That's not all, choosing the right propeller brings with it some sort of a feel-good-factor knowing that you're getting the best from your sailboat. It will give you the peace of mind that you deserve when out there on the water while enhancing your boat's performance and speed.

Unfortunately, choosing the right propeller for your sailboat isn't a walk in the park. If anything, choosing between a folding propeller and feathering propeller brings forth a multi-dimensional problem in terms of the level of performance, efficiency, price, maneuverability, safety, and many more. This is exactly why you should know what they are, what they will do to your boat, and the best one to go for.

Folding Propellers

A folding propeller is essentially a type of propeller that is often mounted at the aft end of a boat's keel. It is designed in such a way that its blades automatically fold out when the engine is used to power the sailboat and fold back when the boat is under sail and the engine isn't working. When the engine is on, folding propellers will spin outwards by a centrifugal force. On the other hand, the water flow forces will push the propellers back when the engine stops.

Folding propellers come in various forms and may range from the most basic types to highly sophisticated geared folding propellers. The most sophisticated ones might be costly but are quite efficient and will provide top-notch performance both ahead and astern while significantly reducing all forms of drags.

We have to note that folding propellers can be ideal for easily driven lightweight sailboats or if you do not want to ignore the unwanted drag and significant loss of speed. Folding blades are also essential in racing circles. They generally fold backward thereby reducing drag significantly and increasing speed and performance under sail.

Benefits of Using Folding Propellers

You've probably been wondering why many sailboat owners have been choosing to use folding propellers on their boats. Well, the benefits that these types of propellers bring to your sailing adventures in terms of speed, performance, and safety are unmatched.

Here are some of the benefits.

Reducing Drag

Numerous tests have consistently shown that folding propellers create the least amount of drag when sailing, especially when compared with feathering propellers or fixed propellers. The two-blade versions of folding propellers are the most efficient in reducing drag, especially when going astern.

Most two-blade folding props can perform just as well as three-blade folding props. However, their simple design of opening independently of each other can sometimes cause imbalances and vibrations, especially if one of the two blades open or close more than the other.

There are also three-blade and four-blade propellers that bring to your sailing game an interesting overdrive characteristic. These blades generally work by reversing automatically when going astern. This feature is important when the engine is on as it can be essential in saving fuel when using the engine to sail in calm conditions.

Folding props generally have better thrust when moving forward than feathering propellers but this will, of course, depend on the pitch as well as the shape of the blades. The prop will go astern if they have a weak point. This is because they rely on the centrifugal force to hold the blades open against the force trying to close them. You have to keep in mind that the blades might not be as efficient as it if going forward if the blades are open.

Offering Safety

The blades of folding propellers don't usually stick out as they do on feathering props or fixed propellers. This means that there are no chances of the prop catching debris or any marine creature. Needless to say, such issues can lead to a loss of steering ability and ultimately cause an accident. In short, your safety is much better if you're using folding propellers.

Greater Maneuverability at the Dock

Folding propellers are generally designed with powerful shapes and hydrodynamic designs that can give your boat greater maneuverability like you would at the sea. These props are designed with superior stopping, forward, and reversing power.

As we noted earlier, folding propellers are the most efficient in reducing drag, which generally affects the speed and performance of your boat. So by installing a folding prop, you will improve your sailing performance and speed by nearly 15%. Your boat will be faster and the voyages will be more enjoyable even in lighter winds.

More Comfort

In an ideal sailing situation when the wind is optimal and the weather is calm, you're likely to hear the sound of the propeller, especially if it's a fixed propeller. The resultant noise can be frustrating but this should be an issue in folding propellers. If anything, the noise levels will be as low as the drag. This is because most folding props are designed with strong built-in shock absorbers to reduce the noise levels.

In short, folding propellers are ideal if you want to reduce noise and vibration that are common in fixed blades.

Great Value for Money

If you've owned a sailboat before, you already know that having a propeller that's designed with various moving parts can be costly in terms of repair and maintenance. This is essentially why many sailboat owners prefer props with just a few moving parts.

As such, folding props can be ideal since their only moving parts are the blades. They are also structured with smooth acting gears and strong materials to ensure durability without any need for greasing, rebuilding, replacements, or maintenance. In essence, folding props will ensure that you spend most of your precious time sailing instead of being at the dock fixing your boat.

Similarly, folding props are known for having lower initial purchasing cost than feathering props. They have a simpler design, which significantly reduces the purchase costs. In short, folding props are more affordable than feathering props.

Cons of Folding Props

Despite these numerous benefits, folding propellers have noticeable downsides that we have to highlight. They include:

• ‍ The fixed pitch that cannot be removed or changed once fitted. If you have to change or remove the pitch, you'll have no choice but to seek the services of a propeller expert.
• Although this may vary depending on the brands, folding props have simple designs that tend to wear out the fastest when compared to feathering props.
• Folding props have inadequate reverse thrust, so you'll have to be very skillful to maneuver tight dock spaces.
• The gears are most likely to be exposed to the marine environment and, therefore, will wear out quickly.

Are Folding Propellers Ideal For Your Boat?

Folding props can be ideal for you if you have a small or medium-sized sailboat with moderate engine power. You'll not only attain extra speed under sail but drag will be a thing of the past. Additionally, folding props can also be ideal for motor sailors and larger boats. So if an extra knot is essential for you, folding props might make much sense.

Again, you'll have the peace of mind knowing that your safety is guaranteed as far as your boat's propeller catching debris or causing an accident is concerned. Its design can prevent seaweed from getting tagged along or anything that might make you lose your steering ability and perhaps cause an accident.

Feathering Propellers

Feathering props operate exactly as the name suggests: the prop blades feather when the engine is on neutral or shut down. They generally feather in the passing water flow in the same way a sail positioned head-to-wind would. It has a small profile that is essential in reducing drag while enhancing speed and sailing performance.

The blades of a feathering prop are designed in such a way that they set themselves perpendicularly to the water flow. This gives them a neutral cutting edge to the water, which makes the blades almost flat. As such, such types of props can be less efficient when sailing ahead since the pitch will be reversed when the engine is going astern. Fortunately, you can repitch your feathering prop by simply adjusting the point at which the flipping blades meet but you'll have to move the gears a couple of notches.

Benefits of Feathering Propellers

Here are some of the benefits of using feathering propellers.

Offers Superb Maneuverability

Generally speaking, feathering props are positive in their function. The blades or the feathering props will be opened by the torque of the shaft. It doesn't matter whether it has seaweed or not, the feathering props will open because of the torque of the shaft that reduces unnecessary shock load. The fact that it has the best thrust in reverse and commendable thrust when moving forward gives it superior maneuverability even in tight docking situations. You'll also not need any skills to maneuver the boat at the dock.

Offers Amazing Reverse

Feathering propellers are widely popular not just because of the superior maneuverability that they bring to your sailing adventures but also because of their incredible reverse features. The blades can rotate 180 degrees in turn of the shaft, thereby giving them a very high level of efficiency on both the reverse and forward thrust.

This will improve your level of control even on the reverse while decreasing prop walk. In essence, the feathering props are much better than fixed props or folding props in reverse. They should, therefore, be your first choice if you're looking for a prop that can give you complete control of your sailboat even in tight spaces. These types of props are also very durable as they're more robust in construction than folding props.

Even though not on the same level as folding props in terms of reducing your boat's drag, feathering props are much better than fixed props. To put it into perspective, a 26-foot sailboat is likely to create about 50 pounds of pull if it has fixed props while the same boat would create 4 pounds of pull if it's fitted with feathering props.

Adjustable Pitch

Unlike folding props that have fixed pitches, feathering props do have pitches that you can easily adjust to optimize the performance of your boat. The systems used by each brand can vary but you can set independent reverse and forward even when on the water. This can also help in reducing the prop walk.

Cons of Feathering Propellers

The most noticeable downside of feathering props is their expensive prices. Feathering props generally cost twice as much as folding props and this can be a major hindrance if you're on a tight budget. You'll also have to service and maintain the props due to their complex designs. Again, you might have to deal with a given level of drag, which makes them less efficient as far as speed and performance are concerned.

Are Feathering Propellers Ideal for Your Boat?

Simply put, feathering props can be ideal for you if you're looking for efficient maneuverability, especially at the dock. These types of props allow you to thrust forward and reverse even in tight docks. As such, this can be a good option for novice sailors as there are no technical skills required to maneuver the boat even in tight conditions.

To this end, we hope that you can make the right decision in choosing between folding propellers and feathering propellers. While they are much better than fixed propellers, the most ideal one for your boat will certainly depend on your specific needs.

Related Articles

Daniel Wade

I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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Better Sailing

Fixed Vs Folding Vs Feathering Propeller

Out of sight, out of mind goes the saying, so it often is for your boat’s propeller. Crucial as this piece of equipment is to your safe and rapid movement from a to b, it often receives very little attention. You simply set it and forget it – until something goes wrong. That’s a shame because most new boats are fitted with fixed-blade propellers as standard, and older boats often have them too. While that is fine when the engine is running ahead, a fixed propeller is inefficient astern. It applies real drag to a boat under sail.

Tests vary in their scientific-ness, but  data suggests that a fixed prop that is locked creates at least 20 times as much drag vs a folding or feathering propeller at 5kt. In speed terms, that equates to some 20% more pace with a folding or feathering propeller vs a fixed one. That data suggests that folding and feathering props are much better than fixed.  Crossing the North Sea from Harwich to Ijmuiden means that it could save you four hours.

Folding or Feathering?

Folding propellers – where the blades close up around the central boss – are marginally more efficient in sailing mode than a feathering prop, that has blades that simply rotate to a position parallel to the direction of movement. This makes them the racer’s choice, but it is a narrow margin and pales into insignificance next to a fixed prop. A feathering prop is nearly as efficient as a folding prop when going ahead and typically a bit better astern. Feathering blades can be more suited to long keel boats where the prop is enclosed, providing insufficient space for a longer folding prop.

On the other hand, a folding prop is less apt to tangle with fishing pots and waterborne debris. In the early days of these designs, folding props could be reluctant to fully deploy when going astern. However, manufacturers claim this tendency has now been eliminated. Tests suggest that they are far more effective astern at high revs rather than low and can cause a loud clunking noise when they deploy. 

Propeller Diameter

This is a measure of the prop’s size and refers to the width of the circle that the blade tips turn through. It is twice the distance from the center of the boss to the tip of a blade. In general, the more powerful your engine, the bigger the prop diameter needed to utilize that power effectively.

Propeller Pitch

The blades of your propeller slant or curve forward (or back in reverse) – this is what part of what generates the motion. This pitch is usually measured in inches and refers to the distance the propeller would advance in one revolution if it gripped the water perfectly. Imagine your prop is a screw; the pitch is how far into the wood the screw advances with one full turn.

The steeper the pitch, the more work the engine must do with each revolution. A standard pitched propeller will ensure that the engine can just reach full rpm at full throttle. Some sailors like being overpitched, however. It puts more strain on the engine, which means it will never reach peak revolutions, but it’ll keep the boat moving a bit faster through the water until peak power. Turning over more slowly, the engine is a bit quieter and more efficient.

Some props have a variable pitch, automatically adjusting to the pace of the boat and revs of the engine. Others allow the pitch to be changed via a turn of a screw on the boss or require the boat to be hauled out.

Prop Blade Number

This is essentially down to you. Fewer blades mean less drag – hence the reason that so many fixed props are two-bladers. But with the exceptionally low resistance of a fixed or a folding prop, this is barely an issue. On the other hand, there can be more vibration with a two-blade model than a three or more blader. And more blades give more power. Most cruising yachts have three blades.

Best Folding and Feathering Props

The Gori is a folding prop that claims to have the thrust of a fixed prop. Made from nickel aluminum bronze, the blades are geared so that they cannot open or close independently. They pivot through 180 degrees to give the same pitch in forward and reverse, which means optimum speeds in both directions. Uniquely, Goris have an ‘overdrive’ function for motor sailing, which deepens the pitch of the prop to give the same power from lower engine rpm.

With the lowest drag of any folding prop, according to some German tests, Goris are used by the Volvo Ocean Race boats and many of the racing one-designs, as well as cruising brands.

Bruntons’ feathering propeller is a technical marvel with either two or three blades that rotate perpendicular to the prop shaft. Because each blade’s weight is offset, they will rotate through 180 degrees between forward and astern, giving them the same optimum pitch in both directions. Free to rotate on their axis, the blades will adopt varying pitches, according to the needs of the boat.

So, when you are motor sailing, they pitch up to account for the driving force of the sails, reducing fuel consumption and engine rpm. This feature should also reduce prop walk astern.

Also manufactured by Bruntons in Essex using high-quality nickel aluminum bronze, the Varifold is designed to appeal to racers and fast cruisers. As a folder, it offers less resistance in sail mode than its Autoprop sister. 

The company claims a unique design for the blades of the prop that cuts noise and vibration. A helical pitch, including reduced pitch towards the blades’ tips, reduces pressure and noisy pulses against the yacht’s hull.

Featherstream

This UK-built propeller is manufactured using aluminum bronze for the hub and stainless for the blades. There is no standard spec for their props because Darglow prefers to talk through a client’s requirements in detail first. 

The pitch on a Featherstream is determined by the pitch cassette installed with it. This can’t be altered when the boat is in the water. Still, it is always possible to send off for a differently pitched cassette from Darglow and install it via a 10-minute operation when the boat is hauled. If you send the old cassette back, this is cost-free. 

The blades are completely flat for frictionless sailing and rotate through 180 degrees for optimum power ahead and astern.

Maxprop blades are flat and pivot through 180 degrees so that the leading edge is presented in both forward and reverse – making for excellent thrust either way. 

Pitch can be changed in 2-degree increments at the turn of a screw, which can even be done in the water with the Easy and the Whisper models. It is not quite the variable pitch that the manufacturer claims, but it does offer some flexibility. The blades are linked by gears, so they open and close at the same time. 

Maxprop says its products are particularly good for catamarans.

Unlike all the other propellers featured here, the blades of the Kiwi Prop are a special nylon-glass composite called Zytel. Glass may seem an odd choice for a propeller. Still, the material is incredibly tough, lighter than metal, and corrosion-free. It is also much cheaper than bronze, a fact reflected in the lower retail prices. The manufacturer also points out that the blades are sacrificial in the event of a collision and much cheaper to replace than potential repairs to the stern gear. 

The blades are fatter than some but symmetrical, free to rotate around their axis for excellent feathering. The boss allows the blade assembly to rotate 100 degrees, offering adjustable pitch ahead and maximum pitch astern for more power at low speeds. 

Kiwi is also developing a two-blade folder. 

This feathering prop is entirely made of 2507 duplex stainless steel for exceptional strength and resistance to corrosion. It features narrow blades that swing through 180 degrees in reverse. 

Pitch is independently set for ahead and astern and can be easily adjusted – as can direction of rotation, if a change of engine necessitates it.

The folding prop from Seahawk is also in stainless steel – but this time low carbon 316 for long life. 

The blades are geared, so they are synchronized, and the bushes can be replaced easily when worn. Plastic bump stops prevent the prop from clunking when it swings open, and the same polyurethane forms side plates to stop metal-on-metal wear. Seahawk provides a five-year warranty.

The Flexofold uses high-quality nickel aluminum bronze in its construction. Being water lubricated, its gears need no grease. Its simplicity and competitive price have made it the go-to prop for many boatbuilders. It has large shock absorbers for quiet opening, and in tests, it performs well both ahead and astern. Also available in a special race variant with a corrosion-free composite boss that saves 2.8kg of weight.

The Variprofile is a robust prop, built to order in ice-class nickel aluminum bronze for an extremely long life. Like most feathering props, the blades are flat and thin, and they rotate 180 degrees in reverse to offer the leading edge in both ahead and astern. A simple turn of a screw is enough to change the pitch, which can be independently set in both directions – ahead, it is all about optimizing thrust, while in reverse, it is about reducing prop walk. A patented multidisc brake acts as a shock absorber to eliminate the clunk when you engage the prop. Its short hub makes the prop really suitable for long keeled boats with a small prop aperture.

Variprofile

Similar to its Variprop, Variprofi le is SPW’s cheaper, small-boat feathering prop. It is mass-produced for modern serial yachts with engines up to 140hp. Otherwise, it has many of the same features as its custom-built sister, including micro-adjustment for the forward and aft pitch.  

Peter is the editor of Better Sailing. He has sailed for countless hours and has maintained his own boats and sailboats for years. After years of trial and error, he decided to start this website to share the knowledge.

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The GORI folding propeller has amassed a record and reputation unmatched throughout the world of propellers for cruising and racing.

Geared blades.

Geared blade design ensures that the blades open and close together giving less vibration ahead and astern.

Gain a Full Knot of Speed

GORI folding propellers reduce total drag by up to 35%. This results in one full knot of improvement in speed under sail.

Full Power Astern

A GORI propeller gives you the optimum thrust in reverse by virtue of it’s propeller blade shape and profile. It does not rely solely on centrifugal force to open the blades as do many other folding propeller types.

History of GORI

Read a brief history of GORI propeller in Seahorse Magazine.

Reduce Drag up to 35%

Increased efficiency +11%, benefits of gori propellers.

• No rotation under sail. No strain or loading to the transmission.
• Blades have both camber & curve (aerofoil) to their shape.
• Increases efficiency (thrust) under power and over a greater Rpm range.
• Lower propeller noise from blade wash due to curve of blade.
• Dramatic reduction in prop-walk (almost non-existent).
• Overdrive function allows for a pitch increase over normal of approx. 2″-3″.
• Simple installation. No gear & blade assembly or pitch settings to make at time of install.

GORI 2-Blade

For shaft and saildrive, with engines up to around 50HP

GORI 3-Blade

For shaft and saildrive, with engines from 10HP to 300+HP

GORI 4-Blade

For shaft and saildrive, with engines over 150HP

For shaft and saildrive, with engines up to 110HP

New from GORI

GORI 3-Blade Single Pitch

No Overdrive For shaft and saildrive, engines from 10HP to 300+HP

Quality Construction

All propellers sold by AB Marine are manufactured from NIBRAL, a metal alloy made of nickel, aluminum and bronze. NIBRAL is far stronger in all specification areas than manganese bronze (commonly used by other prop manufacturers).

Tensile Strength

Impact strength, fatigue strength, 0.2% proof strength, cavitation erosion resistance, corrosion resistance, testimonials.

For the last five years my boat, a Catalina 270, has struggled to get through the water under power, especially against a tide or current. After talking with Geoff at AB-Marine, he suggested a GORI folding propeller. I installed it in the spring and it has made an amazing difference. The speed has increased with less rpm’s, the boat is much more maneuverable and responsive in forward and reverse and I have no trouble making my way through an oncoming current. The new prop has been the best upgrade I have made yet.

– Steve Taylor | Catalina 270

Since it came from the factory six years ago our 46 foot sailboat had a fixed three bladed (speed brake). In a quest for more efficient sailing speeds we recently purchased and installed a GORI 3-blade Folding prop. To our delight our new GORI prop has increased our sailing performance one to two knots and we have also gained over a knot while under power. Soon we will leave San Francisco Bay and begin our cruise to the south and on through the Panama Canal to the Caribbean. With our new GORI prop we will arrive at the fun anchorages even sooner.

– Anna & Steve Sabree | Hunter 46

The Gori 3-Blade propeller has proven invaluable. Our boat’s prop-walk-to-port drove us into neighboring boats until we changed to your 3-blade folding propeller. Now we can easily and safely power in reverse to starboard. Another pleasant surprise was the forward power that a combination of our little 18hp engine and the Gori 3-blade over-drive function provides as they lift our 32ft sailboat’s bow to surge across the bay.

– D. Holden | Beneteau 323

Just want you to know that the 3-blade GORI prop is fantastic! I consistently get at least a 1/2 knot improved performance over my old 2-blade folding prop and the boat doesn’t bog down in head winds & seas. Thanks for steering me to this product, it is worth every cent. Sorry I haven’t had a chance to run flat water RPM sea-trials for you, been too busy racing and doing deliveries to regattas.

– Steven | C&C 115 – Primal Scream

Hi Geoff, I am writing you on route from Newport to Martha’s Vineyard. The GORI 3 blade 15” x 12 x 3 RH propeller has performed beautifully for my Catalina 350 with Universal M35, rated at 35hp, 3000rpm, with the 1.88:1 ratio, RH rotation, 1.00” dia. shaft.  I just want to thank you for your assistance, after what we think was a tressle strike a few days prior to the parade when we discovered that the blade had come off our old Autoprop. Thanks again.

– David Olio | Catalina 350

Would you like to discuss GORI propellers without obligation?

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ENGINE INFORMATION

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Seahawk Low Drag Stainless Steel Feathering and Folding Sailboat and Yacht Propellers

Seahawk's autostream and slipstream propellers have moved to nsw.

Autostream S1/S2 3 blade feathering Yacht propellers

Feathering Propeller Features :

• Strong reverse thrust better than a folding or fixed blade propeller
• All major parts cast in 316 and 2507 stainless steel
• Easy to replace bronze and acetal bushes
• S2 model has a rubber insert to absorb shocks and can be replaced
• Simple external pitch adjustment
• Sizes from 15 to 20 inches diameter
• Rated for up to 75 horse power
• S1 model fits taper shafts up to 1-3/8 inches diameter
• S2 model fits 17 Spline Sail drives
• S2 fits 109mm Gearcase Sail Drives like : Volvo 130/150 and Yanmar SD20 SD31 SD50 SD60
• S2 model does not match : small 89mm Lombardini Sail Drives and small Volvo 120s Sail Drives

Slipstream S5 3 blade folding Yacht propeller

S5 Folding Propeller Features :

• Less chance of catching kelp and ropes than a feathering propeller
• All major parts cast in 316 stainless steel
• Easy to replace bronze blade bushes
• Sizes from 14.5 to 18.5 inches diameter
• S5 model fits taper shafts up to 1-1/2 inches diameter

Slipstream S7 3 blade folding sail drive Yacht propeller

S7 Folding Propeller Features :

• Rubber insert to absorb shocks can be replaced
• S7 model fits 17 spline sail drive shafts like
• Volvo 130/150 and Yanmar SD20 SD31 SD50 SD60

Slipstream S4 2 blade folding Yacht propeller

S4 Folding Propeller Features :

• Less drag than a 3 blade folding or feathering propeller
• Sizes from 14 to 20 inches diameter
• S4 model fits taper shafts up to 1-1/4 inches or 30mm diameter

Slipstream S6 2 blade folding sail drive Yacht propeller

S6 Folding Propeller Features :

• S6 model fits 17 spline sail drive shafts like

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Feathering or folding prop recommendations?

• Thread starter danstanford
• Start date Sep 7, 2019
• Forums for All Owners

danstanford

Wanting to increase our racing results next year and working on the best elements to address. B323 with two blade fixed prop which sings so I have a perfect justification to get it off the boat! Cost is not an issue if it is better. Sailing in fresh water with little risk of snagging lines, but weeds can be a significant issue in some years in some harbors. I want to be able to cruise under power when needed but most of the time the prop is just to get me out into Lake Ontario and back to the dock. For me, prop walk is not an issue though less would not be a problem when I have the rare southerly across my slip causing me to need to back to port out of the slip and down the fairway which can be a challenge. The most important issue for me is the risk of no reverse when I need it and this seems to be a risk with the folding props....is it? In summary, decent motoring and solid reliability is all I need but I really want to increase performance under sail, particularly in light winds. Advice?  

kappykaplan

I like my Maxprop.  

Davidasailor26

We switched from our OEM 3 blade fixed to a 3 blade flex-o-fold a couple seasons ago and love it. The PHRF hit for changing the 3 blade is 9 seconds, but the speed improvement in light winds is minutes not seconds. Prop walk is about 50% of the fixed, just enough so that I can still use it to my advantage when needed, without being overpowering. Speed under engine is basically the same as the fixed prop, maybe 0.1 knots more at cruising RPM. Thrust in reverse is noticably less than the fixed prop, so when I'm coming into the dock and need to slow down I rev to 1200 or 1500 RPMs instead of idle. Never had a problem with it not unfolding. No required periodic maintenance or lubrication; I just polish it quickly each winter. I've read some reports that the 2 blade FOF is more susceptible to vibration issues, so you may want to consider that, but that aside I have nothing bad to say about it.  

My understanding is that a folding prop will be faster sailing and a feathering prop is a better prop especially in reverse. I have a folding and it has been a big improvement. Motoring is fine.  

Reverse is no problem with my Gori 2 blade folding prop.  

Went to a FlexOFold two years ago. Marked improvement in acceleration, and overall boat speed.  

I have had Goris on two boats and am very satisficed with the performance. Equal thrust in forward or reverse, very little prop walk, folds to almost no resistance. Can increase speed from .5 -1.25kts sailing. Another advantage, OVERDRIVE, excellent for motoring if necessary. Will pick up 1kt to 1.5kts boat speed at same RPM.  

DayDreamer41

We have a FlexoFold on our 41 and find no notable performance issues  

Love my Maxprop classic  

• Under sail, prop drag is only a factor for lighter air, where you have insufficient power to overcome friction. In 20 knots, you can drag a bucket behind and it won't slow you below hull-speed.
• In lighter air, you can expect a significant improvement from a folder, and slightly less from a feathering prop, e.g. moving you from 4.5 to 5 kts in a drifting race for a 30 foot boat. How often are you racing in winds under 10 kts in your area?
• If you cruise the boat, what is your decision point for motoring? If I am moving less than 4 kts and I have someplace to go, I'll motor-sail the rest of the way. Usually, I set this number for each passage.
• Based on the studies I've read, folding props are 80% of fixed props for forward, but really lack efficiency in reverse. Feathering props are 90% efficient in both directions, which is even slightly better than a fixed for reverse.
• At slow / docking speeds, a great deal of inefficiency and prop walk can be overcome by changing how you handle the throttle. Expect to learn to handle the boat differently when you get the new prop, but do not let the few minutes of docking determine which prop to buy.
• Most prop manufacturers recommend mounting on stainless steel shafts. If you have bronze, figure in the additional cost of the shaft and labor to replace. Might as well do your cutlass bearing and think about a dripless seal at the same time. $hit adds up!

Parsons said: Under sail, prop drag is only a factor for lighter air, where you have insufficient power to overcome friction. In 20 knots, you can drag a bucket behind and it won't slow you below hull-speed. Click to expand

Parsons said: Based on the studies I've read, folding props are 80% of fixed props for forward, but really lack efficiency in reverse. Feathering props are 90% efficient in both directions, which is even slightly better than a fixed for reverse. Click to expand

Parsons said: Putting together a speed improvement for your boat is a combination of factors, but here are some points that we can discuss: Under sail, prop drag is only a factor for lighter air, where you have insufficient power to overcome friction. In 20 knots, you can drag a bucket behind and it won't slow you below hull-speed. In lighter air, you can expect a significant improvement from a folder, and slightly less from a feathering prop, e.g. moving you from 4.5 to 5 kts in a drifting race for a 30 foot boat. How often are you racing in winds under 10 kts in your area? If you cruise the boat, what is your decision point for motoring? If I am moving less than 4 kts and I have someplace to go, I'll motor-sail the rest of the way. Usually, I set this number for each passage. Based on the studies I've read, folding props are 80% of fixed props for forward, but really lack efficiency in reverse. Feathering props are 90% efficient in both directions, which is even slightly better than a fixed for reverse. At slow / docking speeds, a great deal of inefficiency and prop walk can be overcome by changing how you handle the throttle. Expect to learn to handle the boat differently when you get the new prop, but do not let the few minutes of docking determine which prop to buy. Most prop manufacturers recommend mounting on stainless steel shafts. If you have bronze, figure in the additional cost of the shaft and labor to replace. Might as well do your cutlass bearing and think about a dripless seal at the same time. $hit adds up! BTW: I went through this decision model for a club racer, but mainly cruiser, and it said "Maxprop" and $5,000. How important is that extra knot to you? Click to expand

danstanford said: In the final analysis, an extra knot would be worth $ 5k to me but I am not at all sure I will see that much coming from a two bladed prop! Click to expand

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Low Drag Sailboat Propellers

West by North are specialists in low drag, feathering and folding propellers. We manufacture and supply propellers for any sailing boat, anywhere.

The  Campbell Sailer  propeller is designed and manufactured to be one of the most efficient fixed blade sailboat propellers on the market today. Unique and innovative, it has been granted a Canadian patent.

After nearly thirty years of production and refinement, the Campbell Sailer has proven, against other leading fixed blade designs, to be a superior choice for sailboat owners.

The  Autostream  line of shaft and sail drive feathering propellers provides the ultimate in low drag performance under sail, and high performance under power. Manufactured of quality stainless steel, the service life is a high performance story in and of itself.

From Auckland, New Zealand, the  KiwiProp  is a simple solution to the low resistance feathering yacht propeller.

Features include auto blade alignment with water flow, preventing autorotation for best performance, adjustable pitch  and no gears!

The  Slipstream  folding propeller was designed using many years of collective experience to achieve three main goals: • Outperform competing brands • Provide a long service life, while being user-serviceable • Develop an enhanced product at a competitive price

Sailboat Propellers

Experience the difference....

Uncompromising, Impartial Solutions

King propulsion offers uncompromising and impartial solutions to all your marine propulsion needs.  our unique portfolio of sailboat propellers ensure that we only match the customer with the propeller they need.  folding and feathering propellers have unique characteristics that do not apply to every boat or sailor in them.  we strive to make this connection for you and give you the best technical advice possible. our team are all highly qualified and respected naval architects with countless years of experience in all types and sizes of propulsion systems from sailboats to warships., in addition king propulsion also supports and distributes sigmadrive, and exceptional drive train solution for coupling propeller shafts to engines quietly and efficiently., us distributor for autoprop feathering propellers, varifold folding propellers & sigmadrive, based in usa.

King Propulsion is a US owned and operated company based in Virginia Beach, VA supporting the USA, Canada and the Caribbean.

Tech Support

King Propulsion is staffed by Professional Naval Architects who can meet all of your propulsion needs. From accurately sizing a propeller to shafting and alignment issues, we have you covered.

King Propulsion is a technical consultancy with substantial experience in propeller analysis and propeller design.  King Propulsion represents Bruntons Propellers, a 150 year old propeller company based in the UK.

King Propulsion is an exclusive Bruntons dealer selling the full line of Autoprop propellers, Varifold propellers and SigmaDrives.  King Propulsion also provides full after sales support and propeller refurbishment.

Choosing a Sailboat Propeller

In the market for a new sailboat propeller ow about a folding sailboat propeller a feathering sailboat propeller what about autoprop, they are. supposed to be good or was it varifold, maxprop or gori choosing between them can be an impossible task and understanding the basis of each manufacturers claims and counter claims even harder. at king propulsion we are professional engineers first, technical sales second and we pride ourselves on the fact that we offer all flavors of propeller to suit every boat and every sailor. we don’t need to fiddle facts on propellers, we use science to help you choose what is right for you., if you look at the market you can distill the sailboat propeller types into 3 broad categories, the fixed pitch propeller, the folding propeller and the feathering propeller, each suits a type of sailing, a type of boat and a type of sailor. there is no one propeller to fit all. as any engineer will tell you, design is a compromise to achieve your objectives. so let us look at some of the compromises all the companies don’t want you to know about. the descriptions below are features that transcend the designs to give you some idea of the choices and options available., remember at king propulsion we sell all 3 types of sailboat propeller, so it is all about the right choice for you, propeller drag, the reason sailboat propellers exist in the first place is to reduce the appendage drag of the sailboat and sail faster. each family of designs achieves this in a different way  and compromises on very different parts of the puzzle to get there. for serious racers, this category is the only consideration.  for the regular sailor, it is a choice, low drag, backing performance, motor sailing as you can’t have everything in this category the folders and the feathering propellers fight for the title, autoprop is a bronze medal winner and fixed pitch propellers just add plain old drag., cruising speed at 2500 rpm, not only is the hull shape and the size of the main engine a factor in speed through the water, but propeller type play a big part of this as well.  fixed pitch propellers are the benchmark but autoprop with its self pitching mechanism gets more speed.  the folder and the feathering options are sub optimal here., backing and maneuvering ability, backing down can be one of the most fraught times for a sailboat owner. for some race boats it is not a consideration, for day sailing and backing into tight marina spots it is a requirement., fuel consumption, the wind is of course free, but catching the wind is expensive, especially if you have to motor long island sound or the icw to get to wind. all of the sailboat propellers impact fuel burn in different ways with autoprop the clear winner and the feathering propeller requiring more fuel for the same voyage. the values below are in us gallons per hour., initial cost of the propeller, sailboat propellers are an aspirational product as soon as you move away from the stock fixed pitch propeller. the cost increases as the complexity of the propeller goes up. the folding propellers are the least expensive of the sailboat propellers; the feathering propellers typically the most expensive and autoprop is slightly behind the feathering propellers. these prices are based on 2024 18″ diameter shaft drive propellers., so what type of sailer are you, what type of boat do you have, find out how a sailboat propeller can improve your sailing performance and heighten the sailing experience. simply fill out the form below with basic details about your boat and we will work with you to size and select a propeller that will be a perfect fit for you and the boat, please note, the above data is drawn from actual sea trials, magazine publications and academic research performed by king propulsion and bruntons propellers on their line of fixed, folding and feathering propellers..

Customer Feedback

Our products are in use around the world on a vast array of vessels. here are some of the comments we have had back for our propellers, couplings and service..

Jeanneau Sun Odyssey 43

Halberg Rassy 31

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Accessories

Ewol propellers make maneuvering easier (reduce inertia) and increase sail speed and optimize engine speed.

EWOL adjustable pitch propellers are made of stainless steel alloys that represent the highest technology in terms of marine corrosion and galvanic corrosion resistance, and are also equipped with the most refined technical solutions that make it unparalleled on the market.

EWOL feathering propellers can be fitted on sailing boats with both traditional (endothermic) and electric engines and with both mechanical and hydraulic inverters. The components of EWOL propellers are made of super-duplex stainless steel alloys, developed by the steel industry for extremely heavy tasks.

EWOL regularly presents new versions of its products with increased performance, and is now also working on developing additional innovative products that will come out in the short and medium term. Nowadays, anyone seeking a truly reliable product that performs over time, solves boat manoeuvrability and sailing speed problems, and is always up at the cutting edge of technology and materials, should install an EWOL propeller on their boat.

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Volvo Penta

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Max Prop Easy Sailboat Propeller 3B-15"

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15" Max Prop Easy 3 Blade Propeller - Metric Bores Available, Call For Pricing.

78mm Hub fits shafts 3/4" to 1" and up to 37hp max.

85mm Hub fits shafts 3/4" to 1.125" and up to 47hp max.

90mm Hub fits shafts 3/4" to 1.250" and up to 60hp max.

Vessel data required for order. Click here to submit information.

• The Max-Prop Easy is a true step forward in Max-Prop design. The ease of installation and simple pitch adjustment make this model a great choice for a wide range of boats. The three blade design provides smooth and efficient power.
• The Easy ships fully assembled, making installation similar to a fixed propeller, basically slide it onto the shaft, nut it in place and the propeller is ready to go.
• As with all Max-Prop’s the Easy pitch is adjustable. With the Easy the pitch is adjustable in 2 degree increments, providing the ability to fine tune the loading of the engine. In addition, the pitch can be set for different levels in forward and reverse, giving you the fine control we've been missing in reverse.  Moreover, pitch adjustment can be done in the water as the propeller does not need to be disassembled to change the pitch.

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• Product Code: MAXE15-3B
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