Outboard motor for dingy
For a 10''RIB, I would consider an 8 hp. You should be able to plane with two people and have plenty of power for adverse wind and wave conditions.
I used to have a 3.10 RIB and had both a 15hp and a 3hp aboard. When I just needed to drop the dinghy in for a quick trip, I could pick up the 3hp with one hand and be ready to go in a minute. For longer trips or longer duration, I had the 15 hp on a small davit. I now have just the 8hp Yamaha on an Avon 3.10 and am very satisfied.
I personally strongly favor Yamaha, and if weight is important, would only consider 2 strokes.