1991 Johnson 25hp – Plug Gap???

Bought a used boat/motor…pulled the plugs and they are gapped around .045 —-that doesn’t sound right to me. Everything I can find online is .030 gap.
Plugs are NGK B9HS 10

Any idea from the experts?

Thanks

Pete

Pete .30 is what I find also . I do know that NGK plugs come really close to what the actual gap should be in most cases from the factory. you may want to call your local parts house and ask them also they should have the gap listing or call your local marine shop..

Thank you kind sir.

I’m starting to think this motor has a very interesting background. Drained the lower unit lube – pitch black – don’t know of anyone that makes lube that color. Also, stinks to high heck….I know all gear lubes stink, but this stuff is really obnoxious.

Pitch black is better than pure white when it comes to lower unit oil! I’d say go with the 0.030. You can probably find the compressed service data in a book at the library as well.

Welcome to the 25HP Johnson club. Mine is a 1975.

.30 is was i use to go by when i worked on them as a mechanic but i would use i champion plug way before ngk if i remember right thats what they call for

X2 get rid of those ngk’s

the tag on my ’88 says .30

Spark plug and gaps

http://continuouswave.com/whaler/reference/BRP/SparkPlugChart2008.pdf