Spark plugs

[TimJacobs]

A thoughts on using the champion J6C vs J8C plugs. I thought I read somewhere that OMC updated their recommendation to using the J8C plugs but now I can’t find where I read that. Most resources recommend the J6C. This is on a 1956 Johnson 10 hp outboard.

[frankr]

Nah, J6C would be correct.

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TimJacobs

[joecb]

Or perhaps consider J8C if the motor will be doing mostly slow speed work, like trolling all day. A nice light tan color indicates the right burn. With Champion the larger the number , the hotter the plug. NGK are just the opposite, lower number is hotter.

Joe B

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TimJacobs

[outbdnut2]

Use J6C as the others said. The J8C is a hotter plug. Heat range is all about the temperature of the firing-tip of the spark plug to keep it from fouling. If you get that too hot, you can get early detonation (also known as knock or ping) which is like hitting the piston with a hammer, and can eventually cause damage. It can also shorten spark plug life. Heat range has nothing to do with how hot the motor runs or how fast it goes.
Dave

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TimJacobs

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