1978 evinrude 9.9 wot misfire please help


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Well-known member
Feb 7, 2014
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As the title says 78 9.9 it has a misfire at wot have only run the motor in a test tank or with earmuffs on so far. Starts good idles fairly smooth. The motor has sat for 20 year or so according to the seller. I've cleaned/rebuilt the carb, adjusted the carb/timing sync. New plugs (correct plugs) new water pump, lower unit lube changed. New fuel pump and lines. At wot, it has the misfire, like one of the cylinders is not firing everytime. I have not figured out which cylinder yet, looking for any input. I'm thinking maybe one of the coils is going bad? All wires appear good. Thanks in advance.
Yeah I guess that was a little confusing. I notice the misfire when running with the earmuffs on, allowing me to hear the intermittent cut out in the exhaust. I ran it again tonight and it wasn't as bad, although still, i dont think it runs as smooth overall as it should. Idle is fairly smooth, but could be smoother so maybe it just needs some run time since it's been sitting so long. Or maybe I'm just asking too much from a 44 year old 2 stroke.
I think that's good advice. I'll see how it does out on the water, and go from there. Thanks for the time.