Re: 1973 Mercury 4 hp
Welcome to iboats sundog.
Well, somewhere between $200-400 if you are lucky.
Probably going to need some service on the age related parts like water pump, fuel pump, and carb.
Ignition system likely will need a going through. I a buyer were to take it to a shop, they would likely charge him $100-150 to go through it and get it running well.
It would have been worth a few more bucks 3-5 years ago, when people were spending money for something they perceived as nostalgic or vintage.
The market is extremely weak, so don't expect to sell it fast, unless you are giving it away.
Yeah, its worth what you can get for it, but probably not any more than any other 4-6 hp motor that is over 20 years old.
Good Luck.