Marine

Ultra-efficient looped propeller gets contra-rotating double upgrade

Ultra-efficient looped propeller gets contra-rotating double upgrade
Sharrow stacks propellers into a contra-rotating design for outboards and sterndrives that require them
Sharrow stacks propellers into a contra-rotating design for outboards and sterndrives that require them
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Sharrow stacks propellers into a contra-rotating design for outboards and sterndrives that require them
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Sharrow stacks propellers into a contra-rotating design for outboards and sterndrives that require them
The Sharrow CX looks pretty striking from any angle and looks like an artistic sculpture of a flower or gift bow from this one
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The Sharrow CX looks pretty striking from any angle and looks like an artistic sculpture of a flower or gift bow from this one
Sharrow's twisty loops contra-rotate toward a quieter, more efficient boat ride
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Sharrow's twisty loops contra-rotate toward a quieter, more efficient boat ride
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Sharrow's extraordinary looped propellers were already some 30% more efficient than traditional designs – and now the company has put two of them together into a coaxial, contra-rotating prop that promises to be even more energy-efficient.

The multi-award-winning Sharrow Propeller family is growing. The new Sharrow CX incorporates the company's looped design into a contra-rotating propeller set. The sculptural new prop doubles up on blades with the promise of bringing Sharrow's efficiency-boosting, noise-cutting benefits to the already efficient world of contra-rotating outboards and sterndrives from top names like Volvo and Mercury.

New Atlas' Loz Blain did an excellent job diving into the newly energized world of looped air and sea propellers in a primer just over a year ago. In looking at Sharrow Marine's design, advantages included drastically reduced outboard noise and faster, more efficient on-water performance.

In working to make its unique propeller design available to a wider range of marine drives and, thereby, boats, Sharrow launched the all-new CX for preorder this week. The latest Sharrow features two propellers that rotate around a single shaft in opposite directions. Sharrow offers CX variants built to spec for the Volvo Penta DuoProp sterndrive, Mercury V12 outboard and Bravo III sterndrive, and Suzuki 300 and 350 outboards.

The Sharrow CX looks pretty striking from any angle and looks like an artistic sculpture of a flower or gift bow from this one
The Sharrow CX looks pretty striking from any angle and looks like an artistic sculpture of a flower or gift bow from this one

The contra-rotating propeller is an already-efficient platform for Sharrow's twisty looped blades to call home, dating back over a century in aircraft and over four decades in maritime vessels. Volvo Penta is credited with patenting the first nautical contra-rotating propeller application in 1982 with the DuoProp drive that still serves as one of its brands today. Inspired by the contra-rotating propellers the Swedish navy was using to prevent unwanted rotational movement in torpedoes and improve speed and directional stability, Volvo Penta adapted the design for boat drives.

The contra-rotating propeller is a fairly simple concept that features two propellers rotating in opposite directions around the same shaft. The independent and opposite rotations counter the energy otherwise lost in tangential flow, better focusing it on the thrust that drives the boat. The drive system then runs more efficiently than a comparable single-prop drive, resulting in a vessel with improved acceleration and speed, better fuel efficiency or a combination of both. Volvo also claims handling and tracking improvements.

Beyond a general promise of better efficiency, agility and maneuverability, Sharrow doesn't dig too deep into how its tipless blades might improve upon the benefits already inherent in contra-rotating propulsion. It will definitely be interesting to hear results from the water as to how the two fare together, though.

Sharrow's twisty loops contra-rotate toward a quieter, more efficient boat ride
Sharrow's twisty loops contra-rotate toward a quieter, more efficient boat ride

Sharrow's single props have seen plenty of testing on various marine drives equipped to different vessels, including by third parties such as BoatTest.com. Specific numbers vary by test, but Sharrow claims that its patented props can improve efficiency to the tune of 30 percent more range, boost reverse thrust by 50 percent, and reduce noise dramatically. It has taken home several awards since introducing the propeller in 2020, including a 2023 TIME Best Inventions award and a 2022 Marine Power Innovation Award from Boating magazine.

While Sharrow has never had problems being recognized for innovative design, it doesn't seem destined to get noticed for affordable pricing anytime soon. We noted last year that its US$4,999 MX propeller was roughly 10 times the price of a comparable regular propeller. Adding in a second set of loops to rotate in the opposite direction spikes pricing up between $8,995 and $11,995, depending upon the make/model for which it's specced.

On the plus side, only $100 of that is due on preorder and deliveries won't begin until Spring 2026 (Northern Hemisphere), leaving plenty of time to ponder that additional $8895+. Sharrow CNC-machines the propellers from premium stainless steel alloy in the USA and backs them with a lifetime warranty.

Source: Sharrow Marine

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10 comments
10 comments
geofff
"contra-rotating propeller is a fairly simple concept", so puzzled that a firm patented it? Hope their patent was a very loose, but 12,000US does sound like a monopolistic price tag?

Did Penta really patent a version of a 'normal' contra-rotating propellor, after seeing it used on a torpedo?

Seems innovators for the mass market may spend little time innovating & more time buried under international lawyers' fees?
Nobody
No reason to cost so much. Investment casting of stainless steel has been around over 40 years.
Ranscapture
What’s going to stop someone from 3d printing this and selling it for $200
christopher
The headline is a total LIE. Look at the chart - there's one insignificant speed that these work s tiny fraction better than the comparison*, and IN ALL OTHER CASES, they're *WORSE* than a traditional propeller.

* They didn't explain how they chose their comparison, or what is was - and you can absolutely bet they didn't pick one that was a good performer to compare against!!
Rick O
That price is insane. There would never be a breakeven for most boat owners on fuel costs. Stainless 3D printing exists, they should be able to make a more than strong enough prop for much much cheaper.
michael_dowling
christopher: Yes,I am puzzled by this thing. Numerous people on the net have 3_D printed plastic torroidal props,and their results have been a mixed bag.
jym
1 The 1882 volvo contra rotating prop patents expired 20 years ago.
2. For $200 you won't be able to 3D print a toroidal prop strong enough except maybe for a trolling motor.
3 If you try to sell a copy of their patented toroidal propeller, you should expect a letter from their lawyers.
4 Maybe you 3d print a toroidal propeller in plastic and cast a stainless one via the lost wax process and just clean it up via machining
veryken
Well great — another wonderful product that will get ignored, abandoned, and NEVER GOING MAINSTREAM because it’s too expensive.
Kpar
An interesting concept. I take note that aircraft that use contra-rotating props are known to be EXTREMELY LOUD- the TU-95 Bear bomber, for example. Even planes that fly near one in flight (like our interceptors) are advised to keep their distance, to avoid hearing damage! I wonder if this technology may make the toroidal props attractive enough that they will get cheap enough for widespread use.

Remember how expensive large flat screen TVs used to be?
mediabeing
Fine, just duct them ALL.
No More prop scars on whales, porpoises, manatees or people!