Re: 1974 Evinrude 9.9 won’t idle at low RPMs, need help

[rudderless]

quote outbdnut2:

A couple years ago, I worked on one of these 9.9s for a neighbor and I could not get it to idle and troll decent no matter what I did. The neighbor had put the correct new Champion Spark Plugs in it. Just on a whim, because I ran out of things to try, I put in new NGK spark plugs I had laying around and the motor ran perfect! I couldn’t believe the difference – I had previously also tried another set of new Champions. I also tried Champions that were running perfect in a 1989 15 HP, which is a similar motor and that didn’t work either. I mentioned my experience at the Ask a Member board here and several guys verified that NGK plugs, for some strange reason nobody seemed to know, work much better in those 9.9s than other brands. At $2 to $3 per plug most places, it’s worth a try if you haven’t already. I noticed a couple earlier posts suggesting this.
Dave

I’ve got the ngks in my ’76 omc15 and by looking the center electrode and insulator are slightly smaller in diameter than the champs. Could be illusion but now I’ve got to check it.