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Spark plug problems

Heathcliff48

New member
I have a 1974 Evinrude 9.9 outboard that the top cylinder spark plug keeps going bad. I was going to purchase 2 new coils but I think I might have got some bad spark plug. I have installed a new fuel pump and had carburator cleaned. Can anyone help me?
 
Sparkplugs really do not go bad.---------------There is a problem in the cylinder and not enuff heat is being produced.-------------So check and see if you have spark that will jump a gap of 3/8" or more on both cylinders.-----Is the thermostat in place and working properly ??. ----Have you checked compression ???------Have you checked the reed valves ??
 
I will check everything you addressed here. I can clean my fouled plug and no fire, install a new one and it will fire. Mixture may be a tad rich.
 
The cylinder has weak spark or there is not enough heat produced in the cylinder to keep the sparkplug clean !
 
OK guys, I checked the compression on both cylinders and got 115# on each one. Checked spark on plugs with an ark of 3/8" to 1/2". Checked points, not burnt and gapped right. The only thing I can find is plugs (wrong number) and the gas may be mixed wrong (a tad rich). I am going to get me a set of plugs and some new gas mixed and try it when the weather breaks. Will get back to you and let you know what happens. It only does this under load after I have ran it a while. 50:1 mixture.
 
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Sure why not.------Let us know if the warms up after it has run for a while.-------cylindehead should run at about 140 degrees F.
 
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