Spark Plug Gap (.030 VS .040) Evinrude

rickdb1boat · #1 July 8th, 2002, 06:45 AM

I have a 1991 Evinrude 70HP. I recently gapped my plugs at .030 per some advise that I read on this board. I understand that OMC changed the setting sometime back, for what reason I don't know. It seemed to affect my Idle (Lower) and did not notice any other advantage in doing so! Can someone explain this to me and should I just go back to .040, as it ran well at that setting. I have been Gapping at .040 for years with no problems, but was concerned about doing the right thing for my motor! Any opinions about this would be greatly appreciated.

Thanks, Rick

JB · #2 July 8th, 2002, 06:57 AM

Howdy, Rick.

When gapped at .030 the plugs will last a lot longer before needing to be regapped, will fire reliably on a weaker spark pulse.

All of the "yeah, but"s I have heard have been answered with a recommendation for .030.

Your engine. Do what you please.

Good luck.

rickdb1boat · #3 July 8th, 2002, 09:20 AM

Thanks JB, I was wondering why they would change it after all these years! Seems like mine just ran a little better at Idle at .040. Just want to be sure that I'm doing right for my engine! Who Knows?

Thanks, Rick

seahorse5 · #4 July 8th, 2002, 04:55 PM

They only recommended .040 for a year or two, about 13 years ago. Ever since, it is .030".

Back then they found that with a wide spark gap, above .040" as the plug wears, The RF interference would sometimes give a false alarm signal.

rickdb1boat · #5 July 8th, 2002, 05:50 PM

Thanks Seahorse, I thought it was longer than that! When I set my new plugs at .030, my Idle went down about 100 RPM's and I had to bump up the idle screw to get it back to where it was. Not sure what to think!!?? Seems to run the same when underway. Maybe I'll try another set of plugs and see what happens.

Thanks, Rick