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Hello,
I recently purchased a 1973 Johnson 20 HP (20R73). It started, shifted, and ran fine when we test ran it when I purchased it. As I was going over the motor I decided to replace the spark plugs. I saw online the standard plug in this motor was the Champion UJ4J. I went to Oreilly's and they said it had been superceded by the Champion J4C. So, I bought two of those.
When I got home to take out the old spark plugs, I found the prior owner was using J8C Champions. Can someone tell me what the difference is between these two plugs? Should I continue to use the J8C as it ran fine, or should I use the J4C? Can running the wrong plug cause damage?
Thank you,
Robert
I recently purchased a 1973 Johnson 20 HP (20R73). It started, shifted, and ran fine when we test ran it when I purchased it. As I was going over the motor I decided to replace the spark plugs. I saw online the standard plug in this motor was the Champion UJ4J. I went to Oreilly's and they said it had been superceded by the Champion J4C. So, I bought two of those.
When I got home to take out the old spark plugs, I found the prior owner was using J8C Champions. Can someone tell me what the difference is between these two plugs? Should I continue to use the J8C as it ran fine, or should I use the J4C? Can running the wrong plug cause damage?
Thank you,
Robert
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