An Evinrude fisherman (1936, model 4148) that I have, came fitted with "AC 84-M " spark plugs. I want to get a couple of spares, and have found some "AC M84" plugs. My question is are they basically the same plug, maybe different vintages with the M (marine?) in just a different place? And which way does the heat range go on those plugs, as I have also seen AC M82 and M85 plugs.
Many thanks!
Ross
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