Re: Curious what you guys think..
Family of 3 ... probably okay.
Family of 3 + friend ... a little snug.
Family of 3 + friends ... pretty tight. 5 people on board, and you'll wonder where all the "boat" went.
It's a 15' and it'll get cramped in that cockpit kinda' quick.
Mark Twain's are nice old boats (not top of the line, but nice), and that one looks to be in REALLY nice shape (at least in pictures). If the hull is solid it could be a nice runnin' boat out on the water.
The outboard is an electric shift Johnson: I've owned a few electric shifts (have one now) and I rather like 'em, but they can be kinda' finicky and you have to search for parts for 'em (not been made for MANY years and OMC is out of business). I don't know how many mechanics will work on one anymore, and you really don't know what's wrong with it. Ad says, "just needs carbs" - maybe, but who knows? So, assume (unless he can get it to run for ya') you're buying a motor-less boat. And for what's there - decent, well kept boat and trailer + accessories - $600 might be in the ballpark.
But, I would assume a dead outboard on that boat ...
Welcome aboard.