I have a 10.5ft x 6ft 1/8 inch aluminum air boat 39 inch rake in the hull 22inches deep. Its all home made 25hp kohler chain reduction 52inch Aeroprop 16deg pitch. I use it for bowfishing so it always over loaded plus its a hevy boat.

My problem it it plows water to the point that it almost comes over the front of the boat so i have never been able 2 open it up all the way. I know i can shim the motor to fix this but i am unsure if i need to shim the front of the motor or back or if theres something else im missing. Any and all adivce would b great.

sounds to me like you have too much weight on front of boat. shift as much as you can toward back and check the level of motor to bottom of boat. make sure they are the same. now you have a starting point to lower the front of motor or raise the rear which ever is easiest to raise bow. if the motor and boat is on same level you shouldn't have to shim the motor very much. i had a similar problem and dropped the front too much and went back up two washers and fixed my problem.