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1982 75 HP Evinrude bogs at WOT

P

panaman

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1982 75HP Evinrude bogs at WOT when warmed up. Carbs have been cleaned, changed fuel pump diaphragms, link and sync., checked timing. For the first 10 to 15 minutes it runs good, running at 5500 rpm. When warm it won't go over 5000 rpm and it has no power. Pumping the bulb has no affect. Coils, power pack and stator have been changed. Compression from top to bottom 123,120,115 when hot.
 
What spark plugs are you running, and what is the gap setting?

Describe the appearance of the individual spark plugs as best you can.

Between the 5000 rpm running time and the next 5500 rpm running time, what do you do to the engine if anything?

Or do you simply let it sit and cool off, and if so, does this cool off period cause the 5500 rpm running time to suddenly exist again?
 
I'm running Autolite 2634. The plugs are a little wet but not unlike a 2 cycle, the center porcelain is medium to dark brown with the lowest plug the darkest. Once it warms up it doesn't return to 5500 rpm. The next outing it will go 5500 rpm for a short time. It also felt like it had no power when trying to drive it on the trailer. I checked the timer base resistance and all three wires are in the 18 to 19 ohm range.
 
Before going further, try using Champion QL77JC4 plugs gapped at .040 . This is the original recommended spark plug and gap for that engine. I'm aware that the gap was changed to .030 at some point in the 1990s BUT try the .040 gap first.
 
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