Spark plug confusion 9.9hp

[rjoynt]

I have a 1978 Evinrude 9.9hp. There is a tag on the spark plug wire saying to use Champion L78V. But I always double check. My Clymer book says to use QL77JC4, but the QL78V is recommended for 1985 and later models. The QL78V has the non adjustable gap. It is shorter than the QL77JC4.
My Champion plug book says to use QL82C.
Confused? I am!!!
Can I use the longer plugs?
Thanks
Bob

[outbdnut2]

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

[fleetwin]

Well, if you are using the champions, avoid the surface gap QL78V plugs. Either the Ql77JC4 or the QL82C plugs will work fine. The non inductor versions will work fine as well, and might be less expensive: L77JC4 or L82C, these might be tougher to find though.

[rjoynt]

What about using RL86C? I was tol that these are equivalent to QL82C.

[joesnuffy]

I would give the NGK BR7HS a try even if you decide to run a different plug.

I worked on 3 of these motors and I had all the plugs listed above both champion and ngk. The NGKs worked the best in all the engines. One engine was points, and the other 2 had cd ignitions but different type cd ignitions. The NGKs worked the best giving me the best idle results and the plugs remained fairly clean after several hours of run time. The carb butterfly also has to be timed well for a good idle.

just my 2 cents,
Joe

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