[JohnB]

13 degrees is right. Single or twin, I would go with a 30" setback. It allows you to mount the motor higher, and also puts the prop in cleaner water. The hard part is the bracket mounting height. I would suggest mounting the bracket as low as possible to get the max floatation at rest. When your running, the bracket is completely dry.

Then mount the motor high on the bracket. If you mount the motor at the perfect height for cruise, it might be a little too high for WOT, if you mount it for WOT, it might be a little low for cruise. Even fuel/occupancy load will change. If I have 4 people, a full live well, ice/fish, and a full tank of gas, Mine is mounted a little low, 2 guys, 1/4 tank of gas, empty live well at WOT, I am a little high.

It is hard to get it perfect for all loads/sea conditions.