There is already a place for a mounting bracketon the rear transom, not bothered about speed as long as it moves the boat along, I have been looking at the new four stroke Suzuki 6HP with built in fuel tank,
Not sure what size your boat is so.......on my 22' aluminum hull cuddy I have a 9.9 hp and it will push my boat about 10mph at wot. I would consider this to be a minimum hp, as your boat is heavier I would consider a 15hp
This isn't a topic related to Boating Safety. It is moved to Boat Topics and Questions (not engine topics), which is more appropriate for this discussion.