Max Speed Loss

[Mac549]

Over the years my boat has lost about 8 MPH on top end. The engine has 325 hrs on it and has been carefully maintained. 1991 200 BR, 350 CI Alpha 1 Gen II. I used to hit 49 MPH and know I struggle to get to 41 MPH. The motor runs excellent and has no problem reaching max RPM's. I have not changed props and the boat is configured just as it was. It does not consume oil and is always tuned. Maybe prop slippage, carbon build-up? Any ideas?

 

[Woody]

Over the years my boat has lost about 8 MPH on top end. The engine has 325 hrs on it and has been carefully maintained. 1991 200 BR, 350 CI Alpha 1 Gen II. I used to hit 49 MPH and know I struggle to get to 41 MPH. The motor runs excellent and has no problem reaching max RPM's. I have not changed props and the boat is configured just as it was. It does not consume oil and is always tuned. Maybe prop slippage, carbon build-up? Any ideas?

I would verify that you are really able to reach the same max RPM. If that is correct then something else has changed. Heavier boat...are you carrying more junk, is your hull soaking up some water, did you and your GF put on some weight? Dirty hull? Prop out of spec or damaged? Is your drive trim working correctly allowing you to reach top mph? How do you measure speed, are you sure the speedometer is working correctly?

 

[Scottbenson]

Dirty hull

 

[Mac549]

I can actually push the RPM to 4800 depending on trim angle. The trim seems to be working correctly. The prop has been scuffed a few times. Speed is from GPS and speedo. I think I have added some weight to me and the boat. As far as soaking up some water I am not sure how that happens but all of the things you mention are a possibility. The bottom is clean, could use some wax. How do I check the hull for water?