Spark Plugs for 1935 Evinrude Lighttwin 5hp

[thefatsoundguy]

I acquired a 1935 Evinrude model 4102 with AC88 plugs in it. Alas, the threaded terminal on one of them was corroded and the cap fell right off, rendering attachment of the plug wire next to impossible. The best info I could find recommends AC-G-5 plugs, but I can't find any reference to either plug number. Does anyone have any relevant info? BTW, the plug threads are much larger than any other plug I have...I'm thinking 18mm?

Thanks,
-Shawn

 

[thefatsoundguy]

Re: Spark Plugs for 1935 Evinrude Lighttwin 5hp

Looking in Peter Hunn's "The Old Outboard Book" listed Champion 6M as the proper plug, with a further cross-reference to a newer K15J. A visit to NAPA further listed this as a D14. It is indeed an 18mm thread. Initial testing showed good results...time will tell as to whether I have the correct heat range.