Dingy Outboard Motor
Been there, done that. In summary:
<em>Advantages of the four-stroke:</em>
1. Better fuel economy (approx. 1/3 better).
2. No pre-mixing required (less hassle: ratios, cups, oil, spills, shaking tanks, etc).
3. No smoke/fumes in your eyes & nose.
5. #s 1-4 above result in lower environmental impact: evening marina putting is nicer.
<em>Advantages of the two-stroke:</em>
1. Much lighter/easier to haul around.
2. Less weight = easier planing (with hp being equal: my 8''8" dinghy is max-rated @ 5-6 hp).
3. Primitive design means if you know about "lawn-mowers," easier to tear down and work on yourself.
My friend''s 15-hp 2-stroke Tohatsu (God bless you!) weighs as much as my long-shaft 8-horse 4-stroke Honda. I love my ob, until it''s time to haul it around. It must weigh 60lbs, and all the weight is up in the powerhead. It''s run like a champ without so much as a hiccup, but if something did go wrong with it, I don''t think I could disassemble, repair and get it running again like I could a two-stroke motor (but that''s just my level of mechanical ability).
Your 8'' inflatable is likely rated @ 5hp. A 4-stroke motor will be heavier than a 2-stroke, and the overall weight difference, while still a significantly higher percentage, might still yield an <em>overall</em> weight that is manageable, depending on your age/health.
Regarding planing, I have no experience to offer, except that I did put that Honda on my 8''8" inflatable (this exceeded the rating by about 50%) and twisted open the throttle, but after 4 seconds of white-knuckled, fish-tailing acceleration, I realized how insane of an idea it was, and I''ve since repented. I expect a 5hp 2-stroke will plane your dinghy with 2 adults and some additional payload easily enough; whether a 5hp 4-stroke would, I don''t know.
My 2 cents are on the table.