86 Force 50 loses power after 10 minutes

Just got an 86 Force 50 from an uncle who left it sitting for about 7 years. Starts right up and runs great for about 10 minutes (WOT) then begins to miss, loses power gradually, and finally stops. throttling back once it begins to miss results in very rough low end and rough idle to the point of shutting down. If I sit for 3 minutes it fires right back up and repeats the 10 minutes of fun before missing and losing power again. Have followed this pattern for up to 1-1/2 hours on several occasions. In trying to fix it I have replaced fuel line (and bulb) from tank to engine, replaced both coils, replaced plugs, replaced water pump, tested condensors and points (both are good), and cleaned carburetor twice. Fuel is new, 93 octane, treated with Berryman's and stabilizer. Thought coils were breaking down, then thought it was overheating (based on the sympyoms-- although dropping water on top of engine didn't cause any sizzling) and now wonder about fuel supply. Pumping bulb while running doesn't seem to make a difference. Hope I haven't forgotten anything. Haven't tested compression with gauge, but initially it seems real good.

Re: 86 Force 50 loses power after 10 minutes

GordieDog,<br /><br /> I would definitely check the compression just to know where you are at. I would also use fresh 87 octane gasoline and not 93. That alone could be the reason for your problem. This is quite a controversial topic and you may hear some other opinions on that. This is simply my opinion.<br /><br />Shane

Re: 86 Force 50 loses power after 10 minutes

Is the Valve open on the gas tank?<br /><br />TMD

Re: 86 Force 50 loses power after 10 minutes

Marine Doctor-<br /><br />The vent is open on the tank. I read another posting on a similar topic where someone suggested loosening the entire cap to provide even more ventilation. Any experience with that being helpful?

Re: 86 Force 50 loses power after 10 minutes

Something must be fouling a plug. When the problem occurs...pull out the plugs and see which one is the problem. Then get back to us.<br /><br />It would seem that once your electronic components heat up...something fails.<br /><br />TMD

Re: 86 Force 50 loses power after 10 minutes

Once the problem begins, and after throttling back, pulling the wire from no.1 plug results in the engine continuing to run. Pull no.2 and the engine dies immediately. The plugs don't appear fouled upon visual inspection. I determined that early on, and replaced the coils one at a time beginning with the no.1 coil. Replacing just the no.1 didn't change the problem...then again replacing both didn't either (goodbye to $234.) After doing everything I mentioned in my initial posting the overall performance is a LITTLE better, but overall it's been about like this from the first time I put it in the water.

Re: 86 Force 50 loses power after 10 minutes

Sounds like its time to get a manual and do some wire swapping when the problem happens.<br /><br />Move Trigger wires and stator wires around. Check the results...we would be looking for the top cyl to start working.<br /><br />Trigger wires should be the small ones...Stator wires should be the larger brown ones.<br /><br />TMD

Re: 86 Force 50 loses power after 10 minutes

MD-<br /><br />This engine has a battery breaker point ignition rather than capicitor discharge system, so trigger and stator wires aren't part of the deal, if I'm understanding my set-up correctly. Anyone have any experience with fuel pump problems showing up after running great for awhile? I'm going to test the fuel pump as my next thing, as well as see if by some chance there is something clogging the fuel's entry from tank to line. The gas tank sat around for several years. I cleaned it out before using it, but maybe I missed something.