The deck boat control box was similair to the V172. It had a seperate ignition switch. The control box only controlled the cables. Ignition switch is in the "dash".
David, I used the bolts that came out of the deck boat. SS bolts. I think 5/8 diameter. Fine thread with nylon lock nuts.
The old motor on the V172 used carrige bolts. They were steel bolts and VERY rusty. Actually, one of the heads rusted right off! I think if you use SS, fine threads, and lock nuts you would be just fine.
Back to the tach. I looked at my OLD wiring more. The crusty wire going to the upper terminal was a ground. The bottom one I am not sure. I should have paid more attention when pulling this apart.
Seems like it would of had to have been a 12V source as otherwise there would have been no power coming to the tach. So would that mean that this tach was running off the battery alone and not a "tach signal"?