Re: 1958 evinrude 7.5 fuel mixture?
It's not really an antique. In fact, there are thousands and thousands of those outboards still powering small boats everywhere. Prices range from between about $200 to about $500, with the latter reserved for absolutely pristine ones, complete with a really nice tank.
Up here in Minnesota, they're a sought after outboard by fishermen and duck hunters alike, and they get used.
Generally, Johnson and Evinrude outboards made since 1950 aren't really collector's items. They get boat and sold to be used. Parts are readily available, and they're easy to work on.