2350sx losing speed

[West Lake]

Any ideas why my 2350sx would start gradually lose rpm,s and speed? Engine seems to run fine. I can go full throttle and be at 4000 rpm and at 40mph and then as the engine gets warmer it slows to 3800 rpm,s and 38mph. Before i added a wake tower and a bimini top it would top out at 4200rpm,s and 52 mph.

 

[TilliamWe]

Re: 2350sx losing speed

Fuel delivery would seem the most obvious. However, your WOT RPMs are too low. They were always too low. (I'll assume that 52mph is a misprint and you meant 42mph at 42000 rpms)

 

[West Lake]

Re: 2350sx losing speed

Thank you for the reply. You were correct. I failed to mention that I had started using a fuel additive for ethanol. The filter was filthy! After replacing and also a full service on engine,Oil,filter,out drive the difference was instant. Had the boat out yesterday and she ran awesome.