Most people I know who are looking for an older motor are looking for something with good compression, a motor that has potential. Unless someone is after a fully restored vintage motor, they're looking to spend as little as possible knowing they will do the work themselves.
In my opinion, if you can't work on those old motors yourself, your best bet is to buy a new motor or one still serviced by a dealer.
As a parts motor, if its a solid motor with good compression, I'd say its worth in the $500-600 range. Fully restored, maybe $800 or so. As an unknown parts motor, maybe $50 or so tops. If you know it ran, and its got no major physical damage or corrosion its worth a good bit more.
It can be stored on its side if you wish, make sure to lay it on the non-tiller side, or face down if possible. Doing so will drain the carb and help prevent any fuel in the carb from becoming an issue later if it sits a long time.
A stand would be nice but if your selling it with the stand, it raises the price, if not, build the stand to work on any motor you may have in the future as well.
I built myself three types of stands, the first is a 30" wide stand with a wide footprint for larger motors and test running motors. The second type is only 18" wide, just wide enough to hold most medium size motors, with four casters and long enough legs to be stable These maximize storage space and can serve as stands for minor repairs.
The third type are made of steel, these are for the heaviest motors and to demo any motors that need to be run for the buyer. The stand is wide enough to accommodate a large tub of water and has enough space in the back to hold a fuel tank. This stand also has larger wheels capable of rolling around on any surface.
I don't sell my stands because when one motor sells, there's always another to pull out of storage to sell next.
In recent years, I find its best to just sell it as is, let the buyer deal with getting it ready for their boat.
It seems every time I prep a motor for sale, with a fresh carb overhaul, new water pump, and fresh lower unit seals, it sits for years, and by the time it sells none of what you did matters as the water pump is already a couple years old again and likely taken a set, and the carb gaskets dried out from non use.
I just knock a few bucks off the asking price and list them as they are, beyond checking compression, I don't mess with them. I also find that most older motors that sell end up just sitting around anyhow. Rarely are they being bought by someone who is going to use them daily. Those guys tend to buy new motors.
Every area is different though, it was the opposite where I used to live, I couldn't give a newer motor away but the old stuff was like gold.
I do feel those old motors were better built, most of them will be still running when all of us are long gone and turned to compost.
