I currently own both diesel and gasoline engine boats. I do prefer gasoline. Quiet and very little smell, can run at low speed no problem and when fresh water cooled, very reliable. I think a small four cylinder displacement or semi-displacement gasoline inboard or I/O boat would be very nice. It may not get the fuel mileage that a diesel would but the lower price of the engine as well as the lower price of maintenance and parts would make up for that with the amount of hours most people put on their boats. In the sailboat world, the Atomic 4 has been a mainstay and it's a very sweet engine. A modern engine in the spirit of the Atomic 4 would be very sweet.
Kevin