Cavatation or coupling slip

[Tim Bell]

How do you tell if your prop is cavatating or the drive coupling is slipping?? I have through the hull exhaust so we do not hear the exhaust comming through the water like you normally would when the prop cavatates. It slips just before it plains and then stops slipping. I would think if it were the coupling that it would not stop slipping.

Rinker 206 Captiva
5.0 engine
Alpha 1 gen2 1.62 drive
14.5" 19 pitch aluminum prop

Tim Bell

 

[Texasmark]

Re: Cavatation or coupling slip

Since that is the peak of the load on your propeller, you are on the verge of more slipping as it continues to wear. I assume you have an inboard. I am not familiar with them. I guess the prop is pinned directly to the D. shaft. Is there any kind of slip or overrun clutch in those installations? If you have an overrun clutch like you find in farm implements it may need tightening up.

HTH,
Mark

 

[Tim Bell]

Re: Cavatation or coupling slip

This in a Mrecruiser IO There is no pin, the driveshaft from the lower unit goes into a drive coupling bolted to the engine flywheel.

Tim Bell

 

[smoedog]

Re: Cavatation or coupling slip

make a mark on the prop that lines up with the cotter pin. Go run the **** outta it for a few minutes, raise the drive and see if mark has moved. If so, bad hub.

 

[emilsr]

Re: Cavatation or coupling slip

What you're describing sounds like prop slip....which is perfectly normal.

 

[jestor68]

Re: Cavatation or coupling slip

I suggest a 15.5 diameter prop to stop that slipping. It will generate more initial thrust and push the boat up on plane a lot faster.

 

[Tim Bell]

Re: Cavatation or coupling slip

Thanks guys for the tips. We took the boat to the lake and removed the 19 pitch prop and tried a 25 pitch and BINGO! No more slip. By the RPM it looks like we need a 21 pitch. Sure am glad we will not be removing the engine to change the engine coupling!!!

Tim Bell