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

[David Stanton]

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