3081 or 3087 G23 with H6 stock ballast

[greggmck]

Yes I meant the key way channel. Here is a picture of my broken shaft. If you zoom in you can see the key way channel is cut longer than the prop hub and is long enough to streach all the way to the rear of the strut. This is the failure point. I don't have a picture but the key way channel on the "updated replacement" shafts is shorter and is completely covered by a prop with a 2.5" hub.

Knowing what I have learned I would not be changing props with any shaft that has the longer key way as any issues with the taper junction between the prop hub and the shaft taper can exacerbate the failure. Part of the repair bulletin is to use dye on the shaft taper and prop hub to check for a good fit of the taper of the shaft to the prop hub.

If you do lots of surfing especially with additional ballast (+500lbs) and/or a large crew I would be asking my dealer to preemptively replace the shaft.

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[greggmck]

Gregg, thanks for the quick feedback - I have also been seeing the threads on shaft breakage and it was one of the reasons was looking to keep as close to stock as possible while still hoping to achieve some noise (primary) and gph (secondary) gains. Perhaps I'll give the 17.5" a try - looks like Acme has it labeled as the 3085

I will have a chance to take a look at the shaft tomorrow when I drop off my 210 and will investigate the keyway - appreciate the info

https://acmemarine.com/products/acme-propeller-3085

You are correct. The prop (I think) that would be ideal for the H6, especially for surfing is the 3085. Here is a pic of the prop label.

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[TimmyH79]

Greg, thanks for the pictures, I misunderstood your first post and thought you meant it was bad if the keyway extended past the forward end of the strut not prop hub... ugh. Well I'll ask the dealer about it and see what they think for a proactive replacement... also thanks for the clarification on the model, might actual call ACME because looks like they made you one with special cup - on their website the 3085 is still listed as .075 cup.

[RDT-G23]

I have the 3081 and love it; that said, the more posts I read on this thread - the less pleasure I get while being in my boat - for fear of a prop shaft snapping... Maybe ignorance is bliss... It will be doggone ugly if it happens...ugly, I say.

[Sailfun]

I am not sure about lower RPM increasing fuel usage. There are way to many variables. The ECU is not custom tuned to each boat but rather a learning ECU as most are. To really evaluate any change in fuel burn you need to give the ECU some time with the new prop. I would give it at least 5 hours and 10 would be better. You then need to make sure the boat weight is the same for both tests and you run the same NCRS and NSS settings. You also need to know exactly how much time is spent at idle, cruise, wakeboarding, surfing ect.. What I am really saying is for most users it will be very difficult to evaluate fuel burn changes. I am new to the boat so perhaps there is a way to view actual fue flow in one of the sub menu’s. That would be the best comparison. Lowering RPM lowers fuel burn 98% of the time in FE engines once the ECU has adapted. Hence the reason for very high top gear ratios in modern cars.

[SoCal G-Man]

I am not sure about lower RPM increasing fuel usage. There are way to many variables. The ECU is not custom tuned to each boat but rather a learning ECU as most are. To really evaluate any change in fuel burn you need to give the ECU some time with the new prop. I would give it at least 5 hours and 10 would be better. You then need to make sure the boat weight is the same for both tests and you run the same NCRS and NSS settings. You also need to know exactly how much time is spent at idle, cruise, wakeboarding, surfing ect.. What I am really saying is for most users it will be very difficult to evaluate fuel burn changes. I am new to the boat so perhaps there is a way to view actual fue flow in one of the sub menu’s. That would be the best comparison. Lowering RPM lowers fuel burn 98% of the time in FE engines once the ECU has adapted. Hence the reason for very high top gear ratios in modern cars.

Great points. Testing must be done without riders, as there is no way to guarantee that the ride times, circle backs, etc. will be the same. I believe you can get a very close comparison as long as the water is consistent.

[greggmck]

I am not sure about lower RPM increasing fuel usage. There are way to many variables. The ECU is not custom tuned to each boat but rather a learning ECU as most are. To really evaluate any change in fuel burn you need to give the ECU some time with the new prop. I would give it at least 5 hours and 10 would be better. You then need to make sure the boat weight is the same for both tests and you run the same NCRS and NSS settings. You also need to know exactly how much time is spent at idle, cruise, wakeboarding, surfing ect.. What I am really saying is for most users it will be very difficult to evaluate fuel burn changes. I am new to the boat so perhaps there is a way to view actual fue flow in one of the sub menu’s. That would be the best comparison. Lowering RPM lowers fuel burn 98% of the time in FE engines once the ECU has adapted. Hence the reason for very high top gear ratios in modern cars.

In my post where I published fuel burn I measured the fuel consumption in nearly identical conditions (100% surfing with same weight load) for almost 12 hours and the difference was about .6 Gal / hour. Also a higher gear does lower fuel consumption in a car because once the car/truck is up to speed the inertial load on the engine is reduced. In this case the transmission can shift to a higher gear to reduce engine RPM and the ECU can lower fuel consumption by burning a leaner mixture. But when surfing the load on the engine is very significant. To develop the same power necessary to push a nearly 10,000lb surf boat at lower RPM the ECU MUST increase the fuel to the engine. How else can the engine develop maximum power at lower RPM? If you doubt this try climbing a very long hill pulling a trailer with your car shifted into overdrive. Your fuel consumption will be much greater than if you downshift.