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Spark Plug Question

K

KB9VGD

New member
1991 Evinrude E150GLEIS

I've been using Champion QL77JC4 spark plugs in this engine and it runs okay, but I've been hearing that the Champion QL78YC is a better plug to use. Is this right?
I do a lot of low speed running and it always seems to "cough" once in a while.


Thanks for any info!
 
The Champion is the recommended spark plug. Stick with it. The "cough" at idle indicates a slightly lean mixture (air to fuel), possibly due to one idle air bleed jet being having a ever so slightly larger inside diameter. Keep in mind that the engine wasn't built to be a trolling engine.

If you have the plugs gapped at .030, try setting them to the old recommended gap setting of .040 . That make clear up you low rpm coughing problem.
 
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