From what I have seen and heard, the old Johnsons are built like tanks and last forever, but if something major breaks, parts cost these days can be insane enough to prompt you to "use the engine as an anchor" or "throw it off the nearest bridge" instead of fixing it. I guess if you have the space you could buy a broken "parts motor" and try to get by that way. But for electrical parts you might end up having to bite the bullet anyways and replace that stator ($250-$300) or what have you out of pocket.
From my limited perspetive, there is awesome help here on these boards with Johnson/Evinrude motors. I see less help with Mecury here, although when you're buying parts and labor today it seems there are more places that sell and deal with Mecurys than Evinrude/Johnsons.
Talk to an outboard mechanic they'll tell you to stick with 1990s and newer motors. What is the fascination with the older motors... are you trying to do a period restoration or something? I'd definitely stick to a newer motor if I had the choice.
