I would consider any engine that is reasonably priced, has good compression and overall looks and runs good.
Appearence may be cosmetic but it indicates how well it was taken care of. If its all dinged up, has corrosion spots all over and generally looks like it has been put through the wringer, it probably has.
In your area, saltwater is an issue. Check all the bolts, brackets, zincs, etc.., for signs of bad corrosion. Any signs of barnacles on the foot?, which is an indicator is was kept on a lift for long periods of time, a deal killer for me.
Other than lower unit oil, plugs and an impeller, not to much to replace up-front unless you know it needs it. Maybe fuel lines if they look cracked.
As far as age, depending on looks and how it runs, I would go back as far as the mid-80's if it was in great shape.