Toroidal propellers: gas burn reduction potential?

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I can tell you've thought about this and done your homework. All great questions.
It's a great topic, and one I think there's alot to learn about for sure. I think if the engine is propped right, the OEM engine builders are very accurate with how much fuel they know it will burn at whatever RPM. Id also add that most boats are NOT propped for their best performance in the big picture so, I think theres also that to consider. I think with these props you can gain some efficiency for sure, I just think its not as much as they claim and im putting my money on they compared it with stuff that wasnt right in the first place or could have been alot better. Because your right its prop slip in the end. However that being said Lets go back to RPM real quick. Burn less RPM you burn less fuel. This is not an opinion its a fact. One that is not considered most the time. Especially when dealing with outbards, because they are compact, and they dont start making their torque usually until 4 grand ish. Not saying im 100 percent right, im just a mechanic boat builder who considers the facts and i'm always learning too. Those facts i consider to be fundamentals, because HP equals fuel burn and engine temp. You have your temp, fuel and RPM, that determines how much HP you have outside the crankshaft of that engine. In any combustion engine.

End of the day theres an issue and thats who wants to drive their boats at 40 MPH around here? Maybe on a perfect day but when does that ever happen on a regualar basis? So if these props get you in fact the percentage of fuel savings they are claiming then you would have to be doing 30 MPH at 3000 RPM.

I phone the company and talked with the rep about this and he didnt have an answer for me nor did he understand what I was asking. Nice guy for sure. Id like to see a side by side comparison. Same boat, same everything just the best wheel against one of these and see. I think thats how we get to the bottom of this. Then theres the fragility of these to also consider.





You really would have to get the dyno sheets and compare all the various OEM engines within the same class and compare apples to apples I guess. Thats a long conversation

Torque.

If they have less slip at lower RPM - I'd guess the motor with the best torque can see the most benefit at lower speeds. Be interesting to see this on a diesel outboard, and to see how it compares to a dual prop setup.


Also to see the same prop on 4 motors same hull - Merc 90hp - 2.1L block , Yamaha 90 hp 1.8L block, Suzuki or Honda 1.5 liter block.... Anyone want to send me 100K, I'll get right on the testing..

 

[gvh]

After discussions with their engineering department I decided to give it a shot. I find that as my boat is pretty heavy and when 4 of us are headed out the boat needs at least 4500 rpm to get on step initially and rpm needs to be at least 3200 to hold the speed. I’m told that the on step rpm should drop along with the rpm to hold it. What i would like to see is the boat staying on step at the lower rpm even if the speed if slightly is less and hopefully less prop slip will achieve it.
Will have to wait until April to find out.

 

[Flashman]

I talked to a guy with a Hewes 250 Alaskan running twin 200hp Yamaha's. He put sharrows on. Got 10% better mileage and maybe more interesting he dropped his minium planing speed from something like 20mph to 16 mph. That was more valuable for him than the fuel economy as he found it helpful running in rough water.

 

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I talked to a guy with a Hewes 250 Alaskan running twin 200hp Yamaha's. He put sharrows on. Got 10% better mileage and maybe more interesting he dropped his minium planing speed from something like 20mph to 16 mph. That was more valuable for him than the fuel economy as he found it helpful running in rough water.

I think one of the biggest advantages is being able to hold plane at lower speed!

 

[Aquaholic]

I think one of the biggest advantages is being able to hold plane at lower speed!

Hydrofoil says “we've been doing that for years”.

 

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Hydrofoil says “we've been doing that for years”.

My hydrofoil cost me 1 or 2 knots of top speed. It also stopped my boat from porpoising. Win some lose some.

 

[seabeyond]

My hydrofoil cost me 1 or 2 knots of top speed. It also stopped my boat from porpoising. Win some lose some.

Sharrows may well do that too, just for a lot more cash!

 

[Wondermur]

When I buy a boat with newer outboard that is under powered by most people’s norm and a crying shame based on Stizzlas calculations, one that needs to run at 4700rpm at 24mph then this miracle prop at $1500 is going to be a steeeaaalll compared to swapping outboards.

 

[pescador]

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[kaelc]

Hi Kael —

info.boattest.com

$2000usd sharrows?

 

[seabeyond]

Iinteresting.

Hi Kael —

info.boattest.com

$2000usd sharrows?

 

[SpringVelocity]

Has anyone on this forum used one?

 

[J-GLOBAL]

After reading about it on this forum, I reached out to see if they have a prop for my Suzuki 350 Duoprops.

Coming 2025 or maybe 2026 they said.

We'll see if there's any other tech that 'improves' performance. Happy to give it a go

 

[Marley]

Sharrow MX-A™

Peak performance for 40-200 HP motors. CNC-machined in Detroit from aircraft-grade aluminum. Fits top outboard brands like Mercury & Yamaha.

sharrowmarine.com

Looks like they have props for lower hp engines now as well.

 

[kaelc]

Sharrow MX-A™

Peak performance for 40-200 HP motors. CNC-machined in Detroit from aircraft-grade aluminum. Fits top outboard brands like Mercury & Yamaha.

sharrowmarine.com

Looks like they have props for lower hp engines now as well.

Yup 2500usd for a 200hp and $2000 for the lower hp. I’m going to try a used but new to me prop from a forum member that factory testing said had way better performance than I’ve seen. I wonder how many of their performance numbers are coming from the “perfect” factory prop?

 

[pescador]

Yup 2500usd for a 200hp and $2000 for the lower hp. I’m going to try a used but new to me prop from a forum member that factory testing said had way better performance than I’ve seen. I wonder how many of their performance numbers are coming from the “perfect” factory prop?

1.0. I just hope they have a castle nut that’s not possible to unscrew without a special tool. Thieves will cruise thru marinas at night and make a fortune ripping these off otherwise.

2.0. Where’s the Amazon knock-off?

 

[Aquaholic]

1.0. I just hope they have a castle nut that’s not possible to unscrew without a special tool. Thieves will cruise thru marinas at night and make a fortune ripping these off otherwise.

for that price, they should come with your name or boat reg # embossed in them.

 

[wolf]

Well my current duo prop i can stay on plane at about 3200 rpm . SO if I were to go of shore everyday , maybe but for the cost per trip to fuel saving and the COST of that prop you better be doing well over 200 trips a year just to recoup the cost. Also god help you if you ever hit something as they will bend out of true... BUT hey you will look cool at dock with leg lifted up... to rich for my business...

 

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My uneducated take... more prop/dig may mean you can stay on plane at lower speed and get better economy at certain rpms -- especially if those rpm ranges line up with where the motor runs most efficiently. I can't see this outperforming a dual prop (counter rotating) setup. Or doing much at higher speeds vs a properly propped boat.... I'd love to be proven wrong.

 

[kaelc]

$33 month for their protection plan for normal dings, not sure if it counts if you run up the wrong side of the river in Renfrew or Alberni
https://sharrowmarine.com/products/...elling_plan=4676714786&variant=48691861160226