I agree with the general sentiments expressed, except that we need to realize at some point our custodianship of them will end, for me probably this year. If we sell them to club members or collectors, generally speaking they will go cheap, and the most desireable to us are unrestored, most of us are in this hobby because we are poor and or cheap, with some exceptions.
Therefore to have the best chance of survival for the motors as well as the best price will come from neophytes to the hobby or the general under informed boater. Both will be more attracted to a restored and cosmetically nice motor and will be willing to pay the kind of bucks needed to at least get your money out or make a bit.
Therefore when I buy I will estimate what it will cost to have it cosmetically and mechanically excellent and base my offer on that. I think I will be fortunate to get my initial cost out of my motors because I have not restored and repainted many. One way to go is with a motor made up of mostly salvaged and close to free parts, another thing that some do is to take it to polished aluminum but that takes a lot of time and labor.