Carbon build up on propeller shaft

[stakultexsun]

2025 bayliner vr5 with about 55 hours on it.
4.5 liter 200hp mercruiser with alpha one stem drive.

I've been trying different props to pull me up on a slalom ski. Finally got that going well after 4th prop.

This is a 15" 15 pitch 3 blade EMP propeller. Boat goes 39.5 to 40mph at around 4740rpms, pulls me up on a slalom pretty good after I ihad dealer nstall SE300 hydrofoil.

Anyway, I do notice some vibration at around 2krpms.

I'm guessing the carbon build up is from the exhaust, but I'm also wondering about this prop. I plan to buy a better one now that I know this works... but I'm wondering if this prop is defective or whatever... it's new and paint is peeling off.

See photos and tell me what you think.

 

[stakultexsun]

Also, just had the 100 hour service, they checked engine for codes or faults, none found

 

[cyclops222]

You need a better marina. Did you show them that soot on your finger ? If yes. They are useless as trouble shooters. Look for a better place.

 

[Pmt133]

Vibration around 2k seems normal for a V6. I wouldn't worry about that.

The soot is interesting. I don't know that I ever cleaned inside my hub out but I do know I've never gotten any soot off it... could be normal for EFI. I assume this has catalyst?

 

[stakultexsun]

I think it's actually a 15.25" prop (for the record)

This does have the catalytic converters.

Also, the soot is something I just noticed after the visit to the dealer. I will show them.

On the vibration, it doesn't happen with other props. I'm taking this prop in today for an inspection and/ or exchange.

 

[stakultexsun]

Well, turns out the vibration I'm getting is due to cavitation. It's putting cavitation burns on the prop.

Prop guy wonders if the prop sits too low in the water. His theory makes since. This boat you can't hardly even use the trim unless you're going below 10mph.

The reason I'm using a 15 pitch prop is because this boat won't hardly pull me up on a slalom ski.

Installed a se300 hydrofoil and this boat will pull me with 6 people on board (~1000lbs not counting gear) faster than it ever has with less people. It was vibrating before hydrofoil.


I was wondering if it was a weight balance issue, but maybe this motor and drive are installed to low. Looking into this.

Clearly the boat has the power to get me up with 6 people on the boat.