I have Mariner 2hp. I have owned it for years, and it was second hand when I bought it. It chugs on for ever. I think the only thing I have ever replaced have been an occasional plug, and points. It used in both salt water, and fresh. I do flush it out in fresh water after its had salt water in it.
I had a four stroke Honda on another boat, which performed very well, only problem was it was in a well, and tended to run a little hot. It was also a heavy lump to lift on, and off the yacht.
Guess it depends what you prefer, and the security aspect.
Maurice