will J4C or J6C work as a replacement for J5J

[hitace]

will J4C or J6C work as a replacement for J5J?

 

[JB]

Re: will J4C or J6C work as a replacement for J5J

Either will work. The J4C (replaced the J4J) is a bit cooler. . .suitable for high speed operation, and the J6C is a bit hotter. . .suitable for idle/trolling.

 

[dajohnson53]

Re: will J4C or J6C work as a replacement for J5J

Either will work. The J4C (replaced the J4J) is a bit cooler. . .suitable for high speed operation, and the J6C is a bit hotter. . .suitable for idle/trolling.

On this subject, I've often wondered if the J6C was used for sustained high speed operation (or vice versa - using the J4C for low speed), would it harm the engine, or just not be as good in performance as if the other plug was chosen.

 

[JB]

Re: will J4C or J6C work as a replacement for J5J

The J4 is slightly more likely to foul at low rpm and the J6 is slightly more likely to overheat at high rpm.

Slightly more likely means slightly more.