Re: Spark plug and Gap 1994 Evinrude 175
I think there was an updated recommendation on that engine. Anyway, they're not that much difference between a QL78YC and a QL77JC4: <br />Q is for the inductive resistor.<br />L is the length of the threaded part of the plug (.472")<br />77 or 78 is the heat range. Too cold and the plug will foul, too hot and it's a site for pre-ignition (bad). For champion plugs, heat range goes up with number. NGK goes down. Heat range is specific to an engine. There's very little difference between 77 and 78.<br />Y has a protruding ground, J has a cutback electrode.<br />C indicates a round ground electrode with a sawed gap.<br />4 is the production gap (0.044").<br />NGK uses a different nomenclature, but it works a lot the same way.<br /><br />Like Bradley, I have no warm spot in my heart for Champion plugs, but they do work better in OMC outboards. Oh, and I think you'll find they're a lot cheaper than the proper NGK plugs.<br /><br />Hope this helps!