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1973 18hp Evinrude spark plug type

C

Cretedude

New member
Having trouble finding an alternative spark plug for my 1973 18hp Evinrude two stroke. OME calls for Champion #0378320 L/P. These are no longer made. Does anyone know what plug can be used? I heard Autolite has one but can't find any reference to it. Thanks
 
Thanks for the comments. The difference between the J4 and Autolite 303 is what I call the tail or thread length. The 303 is 19/64 long and the J4 is 27/64 long. Will difference in length effect cylinder combustion and are heat ranges comparable. I use the J4 in my other Johnson motors where marineengine.com refers them,but there wasn't any reference to another plug since the original was no longer made. I've tried to find the specs and dimensions of the original but have not had any luck.
 
I think the J4C, J4J should be the same thread as the Autolite 303. They are interchangeable. I'm gonna head to the shop for a picture to post.
 
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