Why I am losing so much speed

[FoyToy]

2005 SeaRay 200 Sundeck with 5.0 Merc 260HP. My RPM's at full throttle are about 3800 and my speed is limited to 25-28mph. I remember hitting 42 mph when I first bought the bought with passengers. I do usually have a full crew with equipment and dock the boat so I know the crud build up slows it down, but a 17mph loss seems too much. Any thoughts on boosting performance? Thanks All!

 

[SteveRuss]

First, your RPMs are off by about 1000. That's why you are limited to 25-28. This could be the result of a) dirty bottom, b) bad prop, c) bad ignition (check distributor and plugs), d) bad fuel (does she run very rough or seem normal?) Check all the easy things first.

 

[FoyToy]

Prop is fine. Bottom is dirty so I know that's a contributing factor. She does seem to run smooth. I am planning a good tune up this year. THe SeaRay delaer checked it all out and says everything seems to be in order, but I have heard from others that my RPM's shouled be 4600-4800 wide open. The dealer did not mention anything about that.