I had a tohatsu 5 hp propane outboard. (tohatsu makes mercury's small outboards) Started up really easy. Ran a 5 lb tank on mine. It was really quiet (four strokes are) You don't smell of gas when dealing with them. Mine started fine. burns clean, no smell to exhaust. No great benefits to them over a gas job though. Just don't have to worry about fuel spills. Re fuel your tank on land and you don't have to worry so much either.
Thanks for the reply. This boat/motor Combo was won as a prize and the combo showed up with a 5hp Propane Mercury on it so I was asked if i wanted to keep it as is or swap it out for a gas engine. I cannot find much reviews on propane Merc's online so Thanks for your reply!!