This is my first post on this forum however I've been reading reviews for quite a while and have benefited greatly from other users opinions and know how. One piece of information that I've had a hard time running down is what size outboard to put on my 15' self bailing raft (nrs otter). After much research looking at 3.5hp, 5hp and 6hp motors, I ended up buying a 3.5hp Tohatsu long shaft from Storm Chasers Marine down in Seward. At my request, they graciously changed out the stock 7" pitch prop with a 4.5" Pitch, heavy load prop. I took the raft out to Sand Lake this afternoon and was quite impressed with the little motor's performance. With four adults, the frame and about 100lbs of gear onboard, my gps clocked us doing ~3.5 mph at ~15% throttle, just slightly above idle and quiet enough for you to hold a normal conversation. At ~30% throttle, the otter was moving along at ~5.0 mph. At ~60% throttle we were only doing ~5.5mph. The torque of the motor was pulling the back of the raft down roughly 4 inches and we had about 5" of water in the back of the boat coming through the self bailing holes. After seeing this, i believe that any additional horsepower couldn't be utilize with the self bailer. In fact, I wouldn't be surprised if a 2.5hp outboard with the appropriate prop could push the raft at 5+ mph.