I'm from Mount Desert Island and my partner worked on a scallop dragger for awhile so I thought I'd add a little perspective and address some of the thoughts presented earlier in the thread. IF the PMI on this man is correct and he died anywhere near where he was found, he definitely wasn't snowmobiling. It can get chilly out on the water (the rule of thumb is to expect it to be anywhere from 10-20 degrees F colder, plus wind chill), but not so cold that it would be snowing or iced over in June.
Regarding the surgery, if this man was a fisherman, he probably had the money for medical care. Fishermen tend to make pretty good money up here. Not necessarily to the point of being wealthy, but certainly to the point of being able to afford insurance in the 90s.
If he were a fisherman, my partner (who, again, was a fisherman for several years and has spent a good chunk of his life on the water) pointed out that it was odd he was wearing a snowmobiling suit and not oilskins, which is what most fishermen would be wearing. So *probably* not a professional on the job, in other words. Possibly a professional not actually on the job, though, just casually out on his boat.
That being said, his clothing and physical description sounds like a dozen guys I might walk past in the grocery store on any given day; the short, stocky, brown-haired, middle-aged guy dressed in jeans, flannel shirt, rubber boots, and some sort of coat. I know there was speculation he might be from a Mediterranean country, but I don't think that's likely. The description fits so many Mainers.
What I find frustrating is the discrepancy between sources: some say he was wearing a jacket and some a suit, and that kind of makes a big difference in what he might have been doing.
My gut feeling is he is, more or less, a local from somewhere in either Maine or the Canadian Maritimes. The description of the clothing sounds local, and that short, stocky type of dude is common here. Heck, I have a friend who could BE this guy if he wasn't 50 years too young and very much alive. And regarding the lack of a missing persons report that matches him, that doesn't necessarily seem wild to me. People up here can tend to be fairly private, and it's possible he didn't have a lot of connections and when he dropped off the radar nobody noticed until it had been long enough that people just kind of assumed he'd died or moved away.
Which leads me to my most speculative thoughts: if this guy was a loner but had, say, really upset someone, it would not be impossible to make a murder look like an accident. You just take that person out several miles on a boat, push them overboard, and leave. You then tell other people, if they inquire, "Oh, yeah, I heard they moved; I think maybe they had relatives in Florida." I don't think it should be ruled out, and I think locals should be pondering if they knew any short, stocky men in the 40-50 range who suddenly "moved away" without notice in 1990.