Maddog, RecRetec, AAA, NRS, all have different setups for mounting a motor. I made a wooden mount for my 13' Hyside raft so I could run an electric trolling motor for fall lake fishing when the wind comes up. I need to get out and test it!
I would think that a 2 H.P outboard would work out great on that raft of yours. Those are usually under 50lbs total weight and they sip fuel.
Good luck and show us what you end up doing.