New boat

well, the 3 horse outboard i have weighs about 35lbs probably and can push the jon boat, 2 people and gear at around 5 knots on calm water like rivers.. roughly that's about 12mph.

i doubt your 7' boat weighs 15lbs or else i'd extremely dislike her chances of being seaworthy. i'd say you could accommodate a 2hp or a 3 at the most and achieve about 5 knots with it - if it's the efficient design you claim it to be. here's a nice 2hp 4 stroke for only $765 new. 4 strokes are a bit more complicated and harder to repair but they are more reliable. of course, the 2 strokes produce twice as much power as the 4 strokes but they're fuel efficiency and pollution levels, caused by unburned oil in the exhaust gas, arn't too great. yet if simplicity is what you prefer, nothing can be more basic than a 2hp 2 stroke engine - an engine almost anyone can upkeep and maintain by themselves. outboards are so advanced these days you need a damn mechanic to service most of the 4 stroke outboards above the 9.9hp mark. complicated just means that there are more things to go wrong and more tests to conduct when they do.

but overall, i'd recommend a 2hp 2 stroke for your boat if you're just getting out on the weekends and have little mechanical knowledge in this field.