Spark plug question.

[RiverFish]

Getting 1973 Johnson 25 hp ready for spring. I have noticed two different spark plugs from different sources noted as the spark plug to use. Is there a difference between these two spark plugs:

Champion UJ4J and Champion JRC ?

Thanks.

[boatfixer]

You will want to use a champion J8C in that engine. Those others listed are old plug numbers

[hamms-scooter]

Is this the same plug recommended for my 1970 25 hp johnson?

[boatfixer]

Yes it is

[RiverFish]

Boatfixer,

Thank you for your advice. I did just buy the J4C plugs last summer, replacing what was in there previously. I noticed I misspelled the plug number in my previous post, it should have been UJ4J (correct) and J4C (misspelled as JRC).

Do the J8C burn hotter than the J4C? Is there a big difference?

Please excuse my ignorance on the subject of spark plugs.

Thanks for your time.

[boatfixer]

Yes it is hotter. Changes in gasoline over the years have changed some plug recomendations. Remember, leaded regular gasoline was king when that engine was made!

[RiverFish]

Thanks.

[SkunkedAgain]

When in doubt, a good marine dealer that sells/maintains your motor brand will know the correct plug. It's worth asking.

[jellio]

If it calls for a J4C I would go with a J6C....a J8C IMHO is to hot of a plug for that motor and taking the risk of burning it down for a little less smoke and build up is not worth the risk especially if your not using it for trolling around. I would say before just throwing the J8C's in I would try the J6C's first and see how they look.