My previous boat had Mariners, they are Mercs if you didn't know. They were good 2-stroke motors. Other than a stator (sp) voltage regulation problem I found them to be reliable hard charging motors. In fact the only issues I had with those motors where issues shared by all 2-strokes, i.e. They were very load, had crappy fuel economy, smoked on start up, and 2-stroke oil issues.
I now have 4-stroke Yamahas, though I have had them for a much shorter time, so far the only issue I have is with maintanence costs but my wife's boat (fish/ski) with a 4-stroke Merc is also expensive to have serviced.
Oh yea, everyone in the know, knows Fords are crap! JK! Not really!