Sharrow Props - Thoughts?

[Ironworker]

Impressive performance numbers but they aren't cheap. Anybody running these props?

Here is a boat test. The cat at 13,600# is closest to our boats.

https://www.youtube.com/watch?v=MNnB_50Z20I&t=522s


https://www.sharrowmarine.com/

[Tony Meola]

Rick

Looking at their site, it looks like they will not be an option for a 31. The smallest diameter appears to be 25 inches.

[Carl]

I love seeing new technology in props.

But it really seems to cost…5400 for an outboard prop, 10,800 for a pair is pricey in my world. I guess if spending 60 grand each for an outboard that number for a prop seems in line. Seems like if run a good distance there is a return on investment, plus added speed and performance.

Again, in my world just too pricey…for now.

[Yannis]

Carl,

Except for the price, I would like to know who, and how, will be able to mend it if you hit a rock or a sand bar, almost mission impossible ...let alone how much a technician will charge for that!

[John Swick]

Amen Yannis.
A prop repairers nightmare!
Damn pretty technology though.
Happy New Year.
John

[Ironworker]

30% increase in fuel efficiency is huge. At $5 or $6 bucks a gallon for fuel it wouldn't take two long to pay for them.

I hadn't though about the repair issue for the props. Thats certainly a consideration.

I sent them an email regarding props for the 31. I'll post their response.

[Carl]

Carl,

Except for the price, I would like to know who, and how, will be able to mend it if you hit a rock or a sand bar, almost mission impossible ...let alone how much a technician will charge for that!

I thought about that too...reading their website, both they and their affiliates/dealers would repair the props. I'd imagine it would be far from cheap nor would it be quick...so maybe pick up a spare set...you know, just in case.

But as Ironworker mentions...run them long enough the saving "CAN" add up quickly.

Or the other aspect, more than marginal performance increases for not a "HUGE" investment. Think of what people are spending on having 5 outboards hanging off their transoms...would an extra 25K for 10-15% performance increase make them flinch.

Push them to all your friends so there will be competition, with competition comes the need to bring the price down to drive sales. Always a better design or better way to make less expensive.

[ktm_2000]

I'd want to do a bit more research on this

I watched their videos and what was done on boattest.com and the props do seem to be more efficient based upon what they are saying but I don't know if the whole story is being told.
https://boattest.com/Sharrow-Engineering-Propeller

about 1/2 down they do a comparison and show the chart below. What I see in the comparison is that the pitch is different as the test of the sparrow prop can only make 5500rpm at WOT where the yammie prop can do 6000 rpm. It seems to me in the test the sparrow prop is effectively a higher pitch prop and the engine can't produce enough output to do a full 6000 max rpm.

the thought that the boat can get on plane at a considerably lower rpm/ fuel burn is intriguing but I am wondering that the increased/efficient blade are is effective at lower cruise speeds but looses its advantage at higher rpms. You can see it clearly as the lines converge on the chart.


I am curious as a whole lot of hours at cruise could allow a fairly quick payback especially if they produce more of these and the cost per prop goes down in the future as they become more common.

[ktm_2000]

ok further comparisons trying to do apples to apples, comparing the boat at the same speed in kts, it does seem to be more efficient in cruising speeds. What is interesting is that most of that efficiency gain has eroded by 27kts

the sparrow at 23kts /5.0GPH / 3500 RPM vs standard prop 23.9kts / 6.2 GPH / 4000 RPM
the sparrow at 28.2kts / 7.1GPH / 4000 RPM vs standard prop 27.9KTS / 7.7GPH / 4500 RPM

To me if you could dial in an engine / prop combination to run really nice at 23kts, you could have a really efficient combo for a canyon boat which does a lot of hours at cruise.

one of the 3 blade props


sparrow prop

[Tony Meola]

Realizing the boat might be running faster and using less fuel which would normally say the engine is not working as hard. But if the engine can not hit top RPM, then I would think even though, fuel efficiency increases, speed increases, the engine has to be working harder. Which would lead to a shorter engine life.

So why do I feel that I am way off base? Maybe someone could explain how not being able to hit top RPM is the engine not over working.

[ktm_2000]

I originally thought the same as you, if it can't hit max RPM, the prop has a higher load on the engine, watching WOT it bears out as the new design prop is spinning less WOT RPM and burning more fuel which seems to me to be an overloaded situation.

lower RPMs were different, I concentrated on the boat speed as if the tests were equal with the only variable being the prop, the same amount of force should be required to push a hull the same amount of speed. Working the equation backwards, if the actual force exerted is the same, yet the engine input (fuel burnt) is different, leads me to believe the the prop is more efficient and less actual engine output is being lost allowing greater speed for the same amount of fuel being burnt.

the only thing I can come up with is that the load on the engine is variable based upon RPM with it being more efficient lower in the RPM band.

this thing screams like it was developed out of a commercial application with a vessel which needs to cruise at 1 speed all the time.

[ktm_2000]

one more question I don't have an answer for, why does the slope of the line change at a different speed? the new style prop seems to want to plane 1.6kts earlier, I would have thought the hull design would determine when the boat planes?

[Ironworker]

one more question I don't have an answer for, why does the slope of the line change at a different speed? the new style prop seems to want to plane 1.6kts earlier, I would have thought the hull design would determine when the boat planes?

Its being compared to the conventional Yamaha prop in the video. Likely a more true example of the Sharrow prop would be to find the best/most efficient conventional prop for the boat then run the tests against the Sharrow.


Another benefit discussed in the video is better boat handling with outboards. I'm not sure this benefit would be carried over to an inboard boat.

I can say if I got 30% more range/fuel efficiency at 23 kts with the Sharrow prop, I'd give serious consideration to putting them on my boat if they were available.

[Tony Meola]

one more question I don't have an answer for, why does the slope of the line change at a different speed? the new style prop seems to want to plane 1.6kts earlier, I would have thought the hull design would determine when the boat planes?

Maybe it is lifting the stern at a lower speed allowing the boat to plane off faster.

[ktm_2000]

that makes sense

[Tony Meola]

There must be a point of no return, but if you really get that type of improvement, I wonder what you would get if you followed Bob Lilco's method of lowering the engines to change the shaft angle. Reducing the angle makes the props more efficient. That should give you more speed and less fuel consumption.

Problem is at this stage you would have to put too much money into her between the props and the work to reduce the shaft angle there might not be enough return on the investment.