5.8 liter omg loses power at wot

by Paul
(Traverse City MI)

I have a 1995 FourWinns 258 Vista I purchase this summer. I'm the third owner, the first was an engineer for FourWiins who ordered it for his daughter. The second was a auto mechanic and boat enthusiast.

The boat is extremely well taken care of and service properly.

My problem is this; all ten times that we took this boat out, it performed excellently at wot. Running around 4000 to 4200 rep and 34 to 35 MPH, now I can barely hit 3000 rpm and 20 mph. On the last outing I noticed a hesitation when I tried to start it, same at cold or hot. Even with the lift pump acting up we still achieved excellent performance all day, once the engine started. No big deal, I contacted a new marine mechanic who diagnosed it over the phone as a bad lift pump. I took it in, had the pump replaced. Keep in mind, it was just a slight problem, not like we had to crank it for a while to start.

Here's the problem. I have a real hard time believing that this was a coincidence. I believe something happened at the repair center, but what? I don't think it's right to blame the mechanic but being a person who likes to think things through, it baffles me. Any idea's would be helpful.

Thanks.