spark plug question

[54bobby]

i just removed the old plugs from my 1969 25 hp eninrude sportster and found that they are J8C's. i replaced them with J4C's. what is the correct plug for this engine. also, what would be the difference in performence in the 2 plugs? last year was the first this engine has been in the water in 30+ years and i had someone else do the work of replaceing everything (impeller, pump, coils and so on. she ran like a top all year but did take quite a few pulls (maybe 10 or so) to start her when cold. after the first start she is a 1 pull start every time. i was wondering if the j8c plug would contribute to the cold start problem.

 

[Joe Reeves]

Re: spark plug question

The Champion J8C is too hot a plug and could (and usually does) result in melting a piston. Do No use this plug.

Use either the Champion J4C or J6C plug gaped at .030. The J6C plug may provide somewhat improved performance either at idle or full throttle... it varies from engine to engine.

Hard cold starting... Check compression... check spark (with plugs removed), spark should jump a 1/4" gap with a strong blue lightning like flame, a real SNAP!... If you haven't cleaning the carburetor, do so as sitting that length of time, it is surely fouled.

 

[54bobby]

Re: spark plug question

put in a set of j4c's this morning and she fired up on the second pull. purs like a kitten.