Late 80's Mercury, no power out of the hole

[ToX]

Hello all:

I have a late 80's Mercury 2 stroke on my 16ft fiberglass. When I first got it 3 yrs ago, it ran great. This season, when i put the engine in full throttle, it runs at 1/4 of the speed. Until I stand leaning over the bow, the engine will then pick up and I can tilt and get up to full speed. I've replaced impeller, had the lower end taken apart and looked at last season, replaced the prop and it's still the same. Never had this issue before.
Any suggestions would be great, thanks !

ToX

 

[starcraft1982]

Re: Late 80's Mercury, no power out of the hole

What are the rpms saying.Is it running full rpms and speed is just not there?if rpms are good,then id explore a "heavier"boat(ie,wet foam)