1970 Johnson 40hp WOT spark

[changetires]

I have a problem with one cylinder not firing when WOT. Spark check in the yard found good hard spark at the plug but when running WOT goes to one cylinder. Where should I look first for something. Last year replaced coils, wires, plugs, points and condensor. Motor ran great for several trips then it decided to take a dump on me.

 

[changetires]

Re: 1970 Johnson 40hp WOT spark

Nevermind, found the problem to be the new plugs were one heat range off and was fouling one plug at a time.