spark plug diameter

[Ru4rusty2]

i'm going to look at a 10 hp sea horse montgomery ward and i want to test the compression in the motor. what i want to know are there a bunch of different spark plug diameters?
I don't know the year or the model# i looked at a chart of motors and i believe that its a Chrysler 1974,75 or 76

Thanks
Chris

 

[JB]

Re: spark plug diameter

Almost certainly a standard, 14mm plug, Rusty.

BTW, that is a Sea King. Sea Horses are Johnson.