Alans, I ran a 5HP 4 stroke Tohatsu on a
9 ft Avon and although it ran very well I could not get it on plane. The engine was heavy at around 56 lbs and it had an external tank that took up valuable room in the boat. A couple of years ago I heard small 2 stroke were being phsed out so I ran and purchased a brand new 1 year old model Mercury 3.3HP weighing in at 28 lbs with a built in fuel tank. This smaller engine powers the boat just as well if not better than the larger one. I believed the 5hp needed to be reproped for optimum performance. The Tohatsu made it easier to manuever as it had reverse and twist throtle but at 56lbs it needed a lift to get it down from the stern pulpit to the water; the 28 pounder I just lower with one hand while holding myself with the other as I step into the inflatable. Usually the 4,5 and 6HP engines weigh about the same so the considerations will be price, power and the intended use. For a dingui use of just going to and from shore I would look for a light engine. Honda makes a 2HP 4 cycle which is air cooled and used by many cruisers.