TOPIC: Drill outboard mount holes.

I sure hope I'm at the correct place to ask this question. I just finished putting in a new 1 1/2 inch wood transom in my Dad's 1968 Fish N Ski Bowrider boat. The mount bolts that was holding his 50 hp Johnson to the transom was 5/16 inch bolts. What would be the correct diameter drill bit to install new 5/16 engine mount bolt to the new transom? Should it be tight and use a 5/16 drill bit or a little looser like a 11/32nd, 3/8 ect.? The original transom was so rotten that I can't determine the hole size. Thanks for any help and sorry if I'm at the wrong place for this question.

You're good here.
A tight fit is always better. (No comment Jan). Sometimes I would drill the same size hole like you stated and coat the bolts with silicone and pound them through, bolt 'em tight.

63 Sabre wrote: A tight fit is always better. (No comment Jan). Sometimes I would drill the same size hole like you stated and coat the bolts with silicone and pound them through, bolt 'em tight.

I agree, a tight fit is always better but as you get up there in age your bolt may not be as hard as it use to and getting it into a tight hole may be an issue.

All joking aside I agree, I would suggest using a marine grade adhesive like 3m 5200. Apply some to the inside of the hole to assist in slowing down any water penetrating into the new transom. also add some around the outside of the hole before mounting the outboard. Home depot carries small tubes of this product.

Thanks for the good info. Brisco