High Revs Low Speed

taza

Over the season it’s getting worse, been struggling to get up to speed,revs are really high and struggling to reach 25rpm
and when revs reach over 4K you can see white smoke coming from prop area,Engine temp is normal and engine sounds sweet,Oil temp is ok, I thought it might be the props slipping on the hubs but I marked them and their not slipping,is there anything in the outdrive that could slip,The drive is a reconditioned one that got fitted last year.

Ran the engine in neutral at high revs and no smoke, anything else I could check

any help appreciated 

2007 Volvo Penta 5.7Gi-G
Engine Serial No 4012215965
Outdrive DPS-A No 4202203870

2007 Rinker 280 Express

raybo3

Is the boat kept in the water? Is the bottom dirty? It does not take much growth or slime to cause a major loss of speed.

GMSLITHO

Yep my brother text his boat sitting in the slip for a month without moving it now he can only get to about 15 mph we’re going to pull it out Tuesday and clean the bottom .the white smoke may be just a vapor trail 

aero3113

Engine coupler? You can mark that also, make sure you put the mark on the spline, shaft ,rubber and rubber housing.

taza

Checked inside engine when running at high revs, no sign of smoke or burning rubber