So many of your duplicate threads have been merged that no one knows where you started.
Give us a break. The Starcraft forum is the best place for answers on you tin STARCRAFT!
When a bracketed OB is installed, the bracket is typically mounted with the motor higher than a transom mounted motor. On a transom mounted motor, the rule of thumb is the AV plate is even +/- 1 inch with the hull bottom. For bracketed motors, the motor is mounted higher, the more setback, the higher it's mounted until the limit is reached. The limit is determined by the pillow effect of water going under the boat. As a boat gains speed, a pillow of water is created behind the transom which is higher and the AV plate should be even with or slightly lower than the top of the pillow.
What is this in a pic? A kind of representation of what I mean.
You are way ahead if yourself is this is where you plan on mounting the bracket. If a 20" motor is mounted, the bracket would be 5" lower than than a 25" motor. Slow down - You have a lot more measuring to do.