1955 johnson 10hp seahorse

[Danielschultz]

i have been looking around online for recommended spark plugs for this motor and i found this website Johnson which has been very helpful but i noticed something that doesn't make sense the title of the page is for 10 hp johnson motors 49 - 55 and as i scrolled down i found the spark plug recommendation but there is a typo in there i am sure, this is what it says "The recommended spark plug is a Champion J6J, now J6C, however with a well used motor most old time mechanics would recommend a hotter plug, like the J8C especially if you do a lot of trolling. Or if you opt for the NGK brand, go for BR6S-8. These plugs use the 3/8" reach, so do not try to use the 1/2" reach ones off the 9.9hp as the electrodes will become smashed by the top of the piston." ok the title says this is for 10 hp johnson this says the spark plug is a j6c or j8c and they are 3/8" reach but not to use the 1/2" reach off the 9.9hp i might be wrong but the 9.9hp is the 10hp motor i think they only made a 5.5 hp and 10hp nothing inbetween i know they made larger ones. so can someone tell me where the typo is or better yet just what spark plug to use.

 

[HighTrim]

Re: 1955 johnson 10hp seahorse

Use Champion J6Cs

EDIT: Forgot to mention, when he talks about the 9.9, he is referring to the more modern motors. There were no 9.9s back then. FYI though, there was a 7.5hp

 

[nwcove]

Re: 1955 johnson 10hp seahorse

^^^+1. forget all the mumbo jumbo about 9.9 and 10 hp motors. dont go hot with the j8c's!! the j6c is the best all purpose plug for your motor, if you run at wot for extended periods, and dont do much low speed running, you may even consider a j4c