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1996 mercury 4 stroke coils 50 hp

N

NSDON

Advanced Contributor
Carb model 4 cylinder, it’s been breaking down once warm, carbs cleaned, it fouled #4 plug, now has new plugs. Acts to me like a coil breaking down once it heats up. The pee stream is cool, so not overheating?

engine has low hours, clean fuel.

How do you diagnose a bad coil? Where is a good place to get a coil in Canada?

Thanks,
Don
 
Swap # 1 and # 4 coil and report what happens.-----Does spark jump a gap of 3/8" on all 4 leads , yes or no ?----Any dealer and even a Yamaha dealer would have a coil.-----Have some used one here I believe.----Your location ?
 
It has 2 coils, not 4, are they identical? They are for cylinder 1 and 4 and cylinder 2 and 3. There is spark on all 4 cylinders and it starts and runs ok until it gets warmed up.
Thanks for the help.
 
Unit has a lost/wasted spark ignition...1 & 4 fire at same time. Time for compression and leak down test, could be fouling from oil blow by from rings
 
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