RE: Engine and positioning ?
What hull style is it? Flat? Slight V? Hydro?
Can we see a pic of the hull?
A boat with that width will be very stable. My boats are 26-28" x 12-13", and I run ball bearing .46's with no problems.
Without seeing what you have, I'm gonna say that your looking at using a .46 or .61.
Keep us updated. [8D]