Plug Gap for 1967 9.5 HP Johnson

[superflydudebike]

Need correct gap for spark plugs. pulled plugs and one is fouled. Gap set at .025 on one and close to .020 on fouled plug. Seems too small. Anyone have access to correct gap? NGK B8S plugs Thanks.

 

[ezeke]

Re: Plug Gap for 1967 9.5 HP Johnson

The correct and recommended pug is a Champion J4C gapped at .030.

"http://www.boatsetup.com/SparkPlugChart.pdf"

 

[superflydudebike]

Re: Plug Gap for 1967 9.5 HP Johnson

Thanks for the quick response and the link. The link provides info on gap for my 6 HP Fisherman as well. This forum is great. I have a question regarding gap. If gap is too small what occurs? If too large?

 

[F_R]

Re: Plug Gap for 1967 9.5 HP Johnson

The gap is related to the voltage required to arc (spark) across the gap. A narrow gap allows a weak, puny spark. A wide gap forces a higher voltage spark, but at the same time it is putting stress on the ignition system. Way too wide and the ignition system can't develop the voltage required to jump the gap. Remember, it takes a lot higher voltage to fire the plug under compression than it does out in open air.

 

[ezeke]

Re: Plug Gap for 1967 9.5 HP Johnson

Don't think that I ever heard or read that expressed any better, F_R.

 

[dimock44]

Re: Plug Gap for 1967 9.5 HP Johnson

FR that was excellant