Same Problem, new thread....
 

1988 Force, 85 HP. Never given me bit of problems in many years.
Weeks ago, all of a sudden, it does not like WOT for more than 10-15 minutes, then RPM's begin to fall off. I posted the issue, and rebuild the fuel pump. Yah, the screen did have rubber pieces on it, and the diaphram was a not like the new one, but it still looked good. I thought I had fixed the problem until this weekend when I WOT'd it home from the far end of a lake. Problem is less.... sort of, but still there. Squeeze bulb stays hard, Motor still pushes hard at 50-75%, but does not like extended WOT operations. I want to take her to the Q' bay but not with this problem. Any help? It does not misfire, just looses RPM, and if I throttle her back before it stalls, motor just keeps on purring. Desperate to hit the seas.

Remove the engine cover, then remove the flywheel.
I'll bet the magnets and contacts are rusted thus not getting good contact.
Is the engine charging good ?