50’s OMC spark Plugs

[bob-d]

A lot of my motors require J6-J’s. which I have a few pieces of NOS.
Since I have them is it better to use them up, or would I get better performance if I upgrade to the newer J6-C.
Thanks,
Bob D

[Mumbles]

The J plugs with the short ground electrode were meant more for when 30W motor oil was mixed in with the gas. It burnt dirty and left lots of carbon deposits behind. The short electrode was supposed to help burn off this carbon. With thermostat temperature controlled motors and newer oil designed specifically for outboard use, this style of plug was no longer necessary as the newer oils burned a lot cleaner and left fewer deposits behind. That’s when the J6-C’s came out to replace the J6-J plugs. They are the same heat range so I don’t think it would make any difference using them. Myself, I’d go with NGK B6S plugs as they are excellent plugs and I’ve had some bad Champions right out of the box over the years.

[frankr]

J6J has the ground electrode cut off half way across the center electrode, presenting a sharp edge for the spark to jump to. All else being equal, a spark will jump to a sharp edge (or point) easier than to a flat surface. So in theory, the J6J should work better in a motor with less than optimum ignition. Needless to say, you can file the electrode back on the -C and get the same result. Of course, the -J is supposed to resist carbon fouling better, not as big an issue with today’s better oils.

[bob-d]

Thank you gents.
Bob D

[David Bartlett]

Mumbles wrote:

The J plugs with the short ground electrode were meant more for when 30W motor oil was mixed in with the gas. It burnt dirty and left lots of carbon deposits behind. The short electrode was supposed to help burn off this carbon. With thermostat temperature controlled motors and newer oil designed specifically for outboard use, this style of plug was no longer necessary as the newer oils burned a lot cleaner and left fewer deposits behind. That’s when the J6-C’s came out to replace the J6-J plugs. They are the same heat range so I don’t think it would make any difference using them. Myself, I’d go with NGK B6S plugs as they are excellent plugs and I’ve had some bad Champions right out of the box over the years.

I like the NGK also!

David Bartlett
Pine Tree Boating Club Chapter

"I don't fully understand everything I know!"

[Tubs]

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[opposedtwin]

Tubs wrote:

[/postquote

Great advice Tubs!

[Author]

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