on a merc seawater pump (gen 4 engine) that mount right below the mechanical fuel pump on the front of the block there are 2 bolts (upper and lower) what size bolt is the lower? I'm not use itf the hole is stipped or the bolt i'm using is not the right one. It feel like the thread is just barely gripping but as soon as you go to tighen it it just lets go. The good news is there are no bits of metal so i think (i'm praying) its not stripped.

I am pretty sure they are both 7/16's. I know you need a 5/8 wrench to turn them.

7/16 Ø,14 tpi, approx 1" length