My wife and I bought a 2000 Doral 250se with a Mercrusier 454. This
boat has only 67 hours and has not been used in two years. The boat has
been winterized by a local marina. This is the only service that's been
done to it. When driving it to another marina, it seemed a little
sluggish. We were able to plane in about 20 sec. and reach a speed of
42 mph at 3/4 throttle.(3400 rpm) However, with 5 people on board, we
could not plane at all. The best we could do was about 8 knots. We
tried trim tabs and looked for weeds or obstruction on the outdrive.
The engine seems to run very smooth in gear, at idle, up to about 1400
rpms. When 3/4 throttle was applied, the engine seemed to work hard.
(about 3200 rpm). Full throttle didn't change a thing. What are the
possible concerns or problems?

Thank you for any help, Ron