SHARROW PROPELLER ANYONE?

[Commuterfisher]

https://www.sharrowmarine.com/?gclid=Cj0KCQiAlMCOBhCZARIsANLid6ZLH1YqfA-Q5E7f2kSiqBSArKOR2kdHG4AKFEflOnjqfQw5ybUiZawaApAqEALw_wcB

 

Is anyone considering this propeller? Very pricey at 4.9k but looks promising. Better fuel economy and the wake looks amazing. They have a testing and development department. Maybe we can arrange some testing of their props on ski boats.

 

I recently changed my prop on my 2006 SN 206 from the Acme 422 to the OJ 428 4 blade Ski Pro per @Jody_Seal recommendation on Planet Nautique. The consensus is that that wake is better and softer. Hard to tell because the Acme 422 is a great prop.

[Horton]

I asked Will Bush ( chairperson of the tow boat committee ) about those propellers a year or so ago. He pretty much just rolled his eyes at me.

[KRoundy]

:o A $5000 propeller!?!?

[2Valve]

As much as 30% more efficient between 2500-4000 RPM

 

Provides up to 30% greater range

 

Noticeably less vibration

 

Up to 50% more reverse thrust

 

An old sales trick is to never provide specific data.

[Drago]

Should be required in Class C and above tournaments

[jjackkrash]

I would not want to ding one.

[MDB1056]

Ridiculous cost. Maybe for offshore racing boats but for skiing- ridiculous

[BraceMaker]

@MDB1056 The science is real but where it makes sense is only when used alot.

 

I could see if you ran a ski school buying one. It would pay off in a year or so of fuel.

 

It will belong on wake boats. IF you never break props.

 

[aupatking]

A 30% improvement on 2 MPG on a 200 mile round trip would be nice but, as @2Valve points out, up to encompasses a lot. For instance, 1% is still within that “Up to 30%”. At 30% it could pay for itself in one fishing season. At 1%....... eternity. That, and I’d need 2 of them. For my 196, she’s gonna get 10 more Acmes or OJs before she ever sees one of these things

[dvskier]

We call that “bleeding edge technology” . Only for the technocrats.

[thager]

Being a sceptic, I call it "Bull Shat"!

[RGilmore]

One thing I've never seen mentioned here, but Zero-Off is not only super responsive in accelerating, but can ALSO "put on the brakes". It does this by actively ramping down the RPMs enough to create drag with the slower-rotating propeller.

 

So it occurs to me that those large openings in this Sharrow propeller might require a much greater and more abrupt drop in RPM - which would result wider swings between high and low revs from the engine.

 

Not that any of this matters, 'cause I ain't EVER paying $5K for a propeller. Not in THIS lifetime anyway.

[ReallyGottaSki]

Prop is going to need its own theft insurance policy

[BraceMaker]

@RGilmore I think what you're tilting at is that the engine when reducing RPM goes from a net forwards on the prop to a net rearwards force on the prop.

 

Ive never observed this effect.

 

There is a good deal of lash in the system with a gear reduction transmission should the prop ever be effectively crossing the lash you'd feel a thump and you would likely see sheared off propshafts.

 

 

[ALPJr]

With that prop you’ll need to run high test.

[skiinxs]

Zero Off definitely throws on the brakes on high letters at 35.4 jump.

[RGilmore]

@Bracemaker "tilting at"? It's an easy effect to observe. Go out in a Zero-off equipped boat and set the slalom tournament mode to 15.5mph. Now ease your way up to full throttle (shift lever "buried") and head out across the lake. Reach up and start rapidly tapping the UP arrow, noticing how quickly the boat can jump to the next speed each time. You can do this extremely fast - probably two or thee button pushes per second.

 

So NOW, when you're going 36.0mph, reverse the process and start tapping the DOWN arrow as fast as you can, back down to 15.5mph. If you can't observe the amazing braking effect that's happening, due to propeller drag, then this is not a question of "opinion" but rather a question of perception. There's no free-wheeling in the transmission, and when you're rapidly reducing the speed setting, as described above, the speed-sensing system will be forcefully dropping the rpm at the prop as far down as necessary to reach the ever-changing target speed. If that isn't a form of dynamic braking, then I don't know what is.

 

As always, just my opinion - but , in this case, also correct.

[LoopSki]

Would one even fit ? Looks like strut would hit

[RGilmore]

@LoopSki I don't think it will fit any of our boats, not due to the strut, but rather, due to the smallest diameter offered for the "NX Inboard" version being 25" in diameter.

[jjackkrash]

Go WFO and drop it into neutral and see how how fast you slow down. All the drag created by the water on all the running surface is a great break when you subtract 450 HP of forward thrust. Boats on a plane don't "coast" like they are on wheels.

[RGilmore]

@jjackkrash Yeah, our boats will slow down relatively quickly when you throw them into neutral. But what you don't realize is that when you do that, the propeller continues to rotate on it's own in response to the high-pressure water passing underneath the boat. If the propeller simple locked into a non-rotating condition at "WFO", your boat would instantly stand on its nose and possible dive for the bottom.

 

Historically, this is a known cause of a number boat-racing injuries and deaths, due a failed shaft coupling or a broken shaft. When that happens, the shaft slides out through the hull until the propeller jams against the rudder, and then the tremendous drag of the suddenly-stopped prop forces the back end up out of the water and the nose down into the water. If the boat is moving fast enough the nose will catch and the boat can flip end over end.

 

This is why inboard racing boats are required to have stop collars clamped onto their shafts directly below the shaft coupling. When a propeller is suddenly stopped "cold" at high speed the resulting drag is unimaginable. Unless you have actually experienced it first hand, you have no idea how abrupt it can be.

 

https://www.pyiinc.com/shaft-retention-collar.html

 

 

[Andre]

@RGilmore

Just like the video with the kid driving his dad in the course and the boat nose dive at the gates...

[Stevie Boy]

Apart from the issues stated by other people , it is expensive, if you ski where it is likely you could ding your prop 5K a time, No Thankyou !

At least the tried and test props, can be straightened out, I don't know the price difference, but I reckon you could probably buy quite a lot of Gas, it just doesn't make financial senses, can you imagine spending 10k so that you have a spare.

[Bookm_dano]

Neat idea. Probably not cost effective.

We could do some math.

BoatTest.com has results of some in water testing.

20' Bayliner with Merc 150 and three different props.

In the 32 mph range (where I usually ski) they measured 7.8, 7.7, and 7.1 gallons per hour.

Since I got the Mastercraft I've run it 1600 hours and damaged two props.

So, 800 hours per prop; 0.7 GPH less fuel flow; I'm paying about $3.10 a gallon for mid-grade (not going to join the octane discussion just yet); that comes to $1,736. Really less since quite a few of those hours are at idle.

Need to have numbers for a DD inboard since I'm not going to switch to a Bayliner, but this gives me some perspective.

If they can offer it substantially under $2,000 I might start to be interested.

Moot point so far with nothing offered for inboards below 25" as mentioned above.

 

Also I liked @Thager's "sceptic" comment.

[DW]

@Bookm_dano - the pre 3400# / 4k RPM ski boats seem to all average around the 5 GPH range, some very spotty data I have gathered on an SN200 is more in the 6+ range, that would close the gap a bit on the consumption difference so you could knock off a couple hundred on your estimate. Regardless, long payback time.

It would be interesting to see the effect on the wake table. Considering the prop kind of reminds me of an egg beater, might do a really nice job of making a very soft wake.

[jjackkrash]

Our boats have a forward gear; neutral; and a reverse gear, and no active "brakes." Maybe I am confused, but is the claim that ZO does something other than adjust the throttle up or down to control the speed?

 

(For the record, I do, in fact, realize that the prop keeps spinning when you toss it in neutral and the potential consequences of tossing into reverse when on a plane.)

[Drago]

Boats make wakes

Props make prop wash

[Hockdog]

And the wheels on the bus go round and round……..

[RGilmore]

@jjackkrash

Sorry, I can only explain it to you; I can't understand it for you.

[Jordan]

A $5,000 solution to a $300 problem....

 

[UWSkier]

@DW on my 2001 Response with a fat skier in tow (me), at 34 MPH I burn 10 to 12 GPH during a slalom pass depending on what the ZBox is doing with the throttle at the time.