Re: OMC V4 CD iginition spark plugs

[lotec]

For what it’s worth, in the past 35 years I’ve owned a number of the OMC cross-flow V-4s: ’78 85hp, ’84 140hp and currently a 1990 115hp. (probably over 3,000 hours of sea-time running them!) The ’78 and ’84 both called for the surface-gap plugs and ran terribly with them, the plugs would foul and had a very short life-span. I believe the manual called for them specifically to help prevent fouling and having hot-spots on the pistons.

The NGK gapped equivalent has been my plug of choice, I can’t ever remember having a failure or fouled plug since switching to them. (Nor have I melted a piston.) Oddly, I believe the 1990 V-4 manual does specify a gapped plug – so maybe OMC learned something after 21 years of making that motor!

I’m sure Don, Dan or Pappy can give you the complete answer here.