Spark plug gap on 1978 35HP Evinrude

BobRitter · #1 March 28th, 2007, 02:17 PM

My "Clymer" shop manual specifies Champion QL77JC4 with a gap of .040. The Champion book, several other sources and a few experts I have talked to state .030. In fact all sources I can find BUT Clymer indicate .030 for virtually all smaller Evinrudes. Clymer indicates .040 for quite a few. Do they know something that the rest of us don't? All sources seem to agree on the plug but not the gap and a difference of .010 is pretty big. Any thoughts?

ezeke · #2 March 28th, 2007, 03:26 PM

The Clymer manuals have publication dates in the front so you can tell if the charts are up to date.

This link will take you to a chart that is updated to 2005, and it is considered reliable by many:

http://www.boatsetup.com/SparkPlugChart.pdf

Be sure to bookmark that link so you can use it again.8)

BobRitter · #3 March 28th, 2007, 04:16 PM

Thanks. My Clymer manual is late 90s. It's hard to imagine the specs would change that much on an old engine. The chart at the link above shows ALL .030 like all my other sources ( except for .031 for NGK ). I'm just really curious about how Clymers came up with a bunch of .040 values, and with the same plug ID.