Johnson HD25, what year & correct spark plugs?

[jvr440]

I have a Johnson HD25, serial #489636, can someone tell me the exact year? I know they were made from 46-50.

Also what is the correct plug for this motor? It's got Champion J-4J plugs in it now.

Thanks.

 

[JB]

Re: Johnson HD25, what year & correct spark plugs?

You are correct, jvr. That engine was made from 1946 to 1950. Someone will be able to tell you the year from the Serial number.

The correct plug was Champion J6J, which has been replaced with the J6C.

 

[jvr440]

Re: Johnson HD25, what year & correct spark plugs?

Thanks JB for the plug info. Hopefully someone will come alone who can tell me the year.

I'm attempting to get this motor running again after a 40 year nap.

Joe

 

[JB]

Re: Johnson HD25, what year & correct spark plugs?

Check out "Awakening a sleeping outboard" in the Engine FAQs, jvr. That pretty much covers everything.

 

[samo_ott]

Re: Johnson HD25, what year & correct spark plugs?

My book says 489636 is a '43-'45 and they started at 491737 in '46 but that doesn't make sense as the HD-25's were from '46-'50. So the closest guess would be a '46 then in my opinion. Others may differ...

 

[jvr440]

Re: Johnson HD25, what year & correct spark plugs?

Thanks guys, I appreciate the info.