Kenny I used 9/16 X 4. I had to drill out the transom. Then I used 9/16 X 2 on the jack plate to the set back and then 9/16 X 2 1/2 set back to the motor.

It is rock solid. Oh and if you are using large square washers on the inside of the transom, open them up to 5/8............thata way you wont have to curse as much as I did.