Re: whats it worth. i have no idea.
I just bought a 1973 20hp on CL for $220, tiller steer, elect. start, in nice condition.
I bought a pair o 35hp motors, a 1979, and 1980, one a remote control electric start, the other a tiller manual start, both running, one needed a few wires under the hood replaced due to rot. I gave $150 for the pair.
I wouldn't sell either one for less than $500 each.
What something is worth and what someone is willing or able to pay in this economy is often a very different number. I've bought some amazingly clean used motors on Craigslist lately for cheap only because the owner needed cash or they just wouldn't sell.
The bottom line is there's not a lot of money out there right now, and people seem to let go of their hobbies first when money gets tight.
The news keeps saying that the economy is turning around but the deals keep coming and I keep finding super cheap, super nice motors all the time from people who are just trying to make the next house or car payment.
If your motor looks like new, then I'd say it 'should' bring in the $500 t0 $650 range, but it's its worn, repainted, or has any defects at all, then they seem to go on average in the $250 range or less. I bought a mint looking 25hp Tiller steer electric start 1994 Mercury longshaft motor that could pass for new last week for $350, it sat on CL for 6 months with no takers before I emailed and went to look at it. I had seen it listed but didn't need it, it just so happened it was still there when I found a use for it. He had it listed at $450. He dropped a $100 with very little argument. The motor needed nothing.