turbulance

[sprinklerfitter699]

My 40 HP Mariner prop cavitates when trying to plane. Engine revs great in neutral, but in forward the cavitation keep the boat off plane. Any ideas?

 

[racerone]

You did not state whether this is a new installation / different boat or what !----All engines rev great in nuetral too.------------Maybe the prop is wrong or is slipping.-----------Try another known to be good propeller.

 

[sprinklerfitter699]

Sorry. Same boat, motor and prop. Just haven't run it in a couple of years. Lower unit oil was changed first.

 

[racerone]

Try another prop.

 

[galamb]

Is the motor "permanently" bolted to the transom (bolts thru the transom) or are you using the screw in "clamps"? - if using the clamps check to make sure the motor hasn't "crawled" up the transom. An inch or so too high can make a tremendous difference...