Buyer Beware! You get what you pay for!
Stitch & Glue or Craigslist or whatever, the less you pay the cheaper the quality.
I learned the hard way buying a used engine.
Be careful with inflatables, they can have very slow leaks. My high presure inflatable floor goes soft from a slow leak over the period of a few days, and I have yet to find the leak since it is so small. Also be careful about the weight of the engine, I have a 5hp Honda and it weighs 60 lbs, very awkward to lift around so it stays on the dink transom. You can get a 9.8 Nissan 2-stroke at that weight if you can find one. Most 4-strokes are heavy. An 80 lbs inflatable dinghy is heavy to move around too, so be willing to tow it. I only use mine when cruising for multiple days so I am ok with towing, especialyl since I cruise with the engine (motorsail). If you plan to tow you can get a higher HP dink engine and bigger dink for fun filled exploring. I can go quite far and fast with a 9'9" inflatable with 5hp engine, wish it was 6 or 8hp though, but the weight is a problem.