Which Spark Plugs

[bobjones294]

I have a 1961 18 H.P. Evinrude Fastwin. The parts manual said Champion J-4J. Champion books said J8C. I pulled out Champion J6C of the engine. I don't know who to believe.
Regards, Bobjones

 

[emckelvy]

Re: Which Spark Plugs

While the 18hp probably isn't that picky about heat range, the correct plug for the application is a J4C. The newer copper-core plug (thus the "C") replaces the old J4J.

Maybe the previous owner did a lot of trolling and needed a hotter plug, you never know! Regardless, an ignition system in good shape will have no trouble keeping a set of J4C's sparking.

HTH.............ed

 

[Faztbullet]

Re: Which Spark Plugs

From the BRP sparkplug chart......

Spark Plug Application Chart for Evinrude & Johnson Outboards
1952 thru 2008
18hp............................1957 - 1973..............J4C.............. .030 gap

 

[lindy46]

Re: Which Spark Plugs

J4C or J6C will work OK. I do a lot of trolling so usually use the J6C. J8C is a little too hot.

 

[seahorse5]

Re: Which Spark Plugs

Here is the official BRP factory chart for J-E sparkplugs:

http://continuouswave.com/whaler/reference/BRP/SparkPlugChart2008.pdf

 

[JB]

Re: Which Spark Plugs

J6C is commonly used for extended low speed operation. It has less tendency to foul. J4C is better for cruising and high speed operation. I always used J4C in my '62 Johnny 18.