Re: Spark plug confusion 9.9hp

[David Stanton]

I’ve worked on 9.9s that for some reason don’t idle good with any of those Champion spark plugs, but magically idle and troll perfect with NGK’s. I posted a couple years ago here about that and others had the same experience, but nobody seemed to know why. Below is a chart that calls out NGK #BR7HS for your 9.9, gapped at .030. Note that the 7 designates heat range and they get hotter as this number gets smaller. I quit using Champions for 9.9 and 15 Johnsons.
Dave

http://www.iboats.com/Evinrude-NGK-Spark-Plugs/dm/cart_id.580398105–session_id.172062052–view_id.669915