My buddy had a friend helping him get his boat ready and inadvertently hooked the battery cables backwards on one battery .
so two batteries and a new perko switch later he has no power. I said id look at it for him figuring it was a blown breaker somewhere. Ithink its the fuse on the starter , but would like to test before removal as it looks like a beech.

Yep - check fuse on starter terminal. White block typically.

I can see it in there , 12 volts with key on to back side?

I hope the boat isn't efi.

Well of course it is , lol.
none of the breakers were blown on the engine if that means anything, but nothing other than trim pump which is direct wired works.

not all Merc has the 90 amp fuse at the starter

Also is this a carb app or MPI ? Year and model and engine serial # ?

Also you have to check battery cables out very closely along with any wires and or any wiring harness portion that could have melted. Some of this depends on what year and app along with how it was fused / relayed / wired and so on.

Hey john thanks, I'll get the serial# in the morning . Boat is 95 cobalt with a 502 efi mefi 1.

Okay, got the engine serial number oko21561
moved trim pump to gain some access to the starter, dang could they put this fuse in a worse place!

Update checked and removed fuse , its toast, see if I can get a new one locally and go from there.

http://www.marineengine.com/parts/me...021E8KS/2336_1

yes as you said it should have the 90 amp starter fuse