92 force 150 hp rpms drops

[linden nj]

I have a 1992 force 150 hp on a 20' boat. Starts runs good, when running at 4800 rpm for 10 minutes, it will nock down to 3000 rpms and serge. I back the throtal off to 1/2 way and the boat will run fine at 3000 rpms and still idol well. I turn the motor off and wait a few seconds, restart it, push down the throtal, it goes back up on plain at 4800 rpms again but only for a minute or two. Then it nocks down to 3000rpms and starts all over again. If I fish for 20 minutes the motor seems to cool down, and I can get back up on plain for another 10 minutes or so. And then it starts all over again.
I did everything amaginable with the fuel system. I know it is not a fuel problem. Does anyone know what piece of the electrical component would get hot and cause this problem.

 

[Frank Acampora]

Re: 92 force 150 hp rpms drops

If you have indeed eliminated the fuel system, then yes, electrical would be the next suspect'

What you are describing sounds like a classic condenser failure mode. Condenser gets hot and shorts, cools down and functions again until it heats up.

Next time it happens, check each plug wire with an inductive timing light. If one plug is not firing, that would be the CD box to check (CD = Capacitor Discharge = Condenser Discharge.) The CD boxes have a capacitor in each side to fire the respective coil.

If that is good, then, since heat rises, the next thing to check would be the stator. It has three windings to charge the three boxes and an intermittant short will affect either one or two cylinders.

The last and least likely suspects would be the triggers and coils.