Another thing to point out, is the fact that the other guy wants to trade his merc for a 'Rude, that is otherwise equal (although I think in this case, the Evinrude is a 25, and the merc is a 20, right? I can't remember). Obviously, the Merc owner thinks more highly of the 'Rude than his merc.
As far as mercs go, there are a number of reasons. Most of y'all know I piddle around with classic and antique outboards quite a bit. Before named Mercury, that company was Kiekhafeur (spelled wrong - I know) outboards, and Carl Kiekhafeur had a passion for the big picture, but couldn't care less about details. So, especially the real old ones, had some absolutely weird stuff. Mixing fine and course thread bolts, when 2 of the same should have been used etc. I believe you even had to pull the powerhead to replace the water pump impeller on a couple models, and on others, special tools are required. Towards the 70s, they got better, but aren't up to my standards. They were still rendered as being a lot more finicky and not quite as reliable in the 70s as the Evinrude/Johnson counterpart. But, they are extremely light and fast, due to a number of things. Some years in the 60s or so, they achieved the max hp with a much higher rpm, giving them an excellent strength to weight ratio, but also having stuff die a heck of a lot quicker. Other years used a number of factors to make them lighter. A common saying among outboard gurus working on 70s and before motors is "Go black [Mercury] if you have to get there quick, go white [Johnson] if you have to get there." Parts are probably more available for the 'Rude, as they would use the same part on 10 or more model year outboards, and on as many hps as possible, whereas mercs changed more often.
If I was to get into racing hydroplanes and such in the under 25 horse category, I would more than likely start with an older merc powerhead and lower unit, and go from there. But, needing a reliable fishing motor, I chose Evinrude/Johnson.
But again, it is really a matter of personal preference. I know some people who are die hard merc people (again, not talking about new motors) and love to cope with some of the weird stuff on them, and work them just right, but that too, is just a passion for working on mercs, that I don't have, and probably won't ever have.
