What size spark plug does a 2004 50hp 4 stroke efi use? 12mm or 14mm?

Question

I need to rethread a spark plug hole and don't know what size tap to buy. Also if anybody has ever used a tool called the Back-tap, I would appreciate any feedback on it. Thank You in advance.

Answer 1

Never heard of this back tap but it certainly looks like a smart idea.

http://www.back-tap.com/

You should have a spark plug handy, just measure it.

12 mm = 0.47" = 15/32"   14 mm = 0.55 " = 35/64

Answer 2

kind of looks like a keen cert, which come with the drill and tap in the kit, and those work pretty well. 14mm is most common but measure old plug to be certain.