Force 7.5HP surging at WOT

[fishrdan]

I have an 89 Force 7.5HP (Gamefisher 225.581751) that surges at WOT. The engine starts fine, idles and runs at part throttle fine, but while at WOT and the boat on plane, the engine bogs down. When I squeeze the primer bulb it picks up again, but then bogs out 15 seconds later. If I slowly squeeze the primer bulb every 10 seconds it runs properly. I saw this problem a few times on 1 trip, it ran fine for a year, then on the last trip the problem came back. Seems to be a fuel delivery problem.

The fuel pump primer bulb and hose is 2 years old and I checked to make sure the tank vent was open. I'm under the impression the fuel pump diaphragm (P/N 818043A1) is bad, but is there anything else I should check/replace while working on this problem? Should I replace the fuel plate reed plate (P/N 2A24757) or fuel pump reeds, do these go bad often?



A bit of history on the outboard; when I bought it 2 years ago it was in pristine condition since the PO hardly used it, bad health. At that time I replaced the impeller and lower unit lube, and it ran great. I took it up to 9000' elevation and replaced the main jet, then swapped back so the carb has been off 2 times. I checked all connections on the carb and they are tight and the carb looks very clean.

Thanks,
Dan

 

[jerryjerry05]

Re: Force 7.5HP surging at WOT

Rebuild the fuel pump.Then (even if it's new) try another squeezie.I have bought BAD primer bulbs right off the shelf.With the new fuels they don't seem to last.The best ones are the ones OMC/Mercrury/Yamaha sell.
Tempo is not the most reliable.
The last 10 years on my boat I have twins and have had to replace about every 2-3 years.Jerry

 

[fishrdan]

Re: Force 7.5HP surging at WOT

Thanks Jerry,

I pulled the fuel pump a part and the reeds looked in real nice condition, but the diaphragm has seen it's better days. I'm guessing ethanol is hard on those old rubber parts.

Luckily, I found the parts locally (big surprise to me) and I'll see how it runs this evening.

 

[fishrdan]

Re: Force 7.5HP surging at WOT

Update:

I installed the fuel pump diaphragm, put the outboard into a test tank, connected the fuel hose, pumped the primer bulb and noticed the quick connect fitting leaking a bit once pumped up and pressurized. If fuel can leak out then air can leak in, found the problem. I was able to scrounge another O-ring in the garage and replaced the bad one in the quick connect fitting. Purred like a kitten for 1/2 hour in the test task, 1/2 that time while in gear. We'll see how it does at WOT on the lake.