Dad's Old Johnson Sea Horse

This is my Dad's old Johnson Sea Horse boat motor/engine. Great story behind how we got it. When I was a kid in the 1970s, we used to rent a cottage at a local lake community in Florida every year. The lake was small and over the years, we got to know all of the locals quite well. There was a story being told around the lake about a motor that had come off the transom of a boat and gone to the bottom of the lake years and years and years before. Well, my Dad was newly into scuba diving and he decided he was going to try and find it. The lake was only about 35 feet at the deepest - where the motor had gone down - and was a crystal-clear, spring-fed lake but very, very muddy and dark at the bottom. Dad searched for that motor using an anchor and rope/knot system. The rope was tied to the anchor at one end and Dad put a knot in the rope about every five feet. He put the anchor down and started swimming circles around it, feeling in the mud as he went along. After completing a circle, he'd move out a little further to the next knot and make another circle. Lather, rinse, repeat. I don't remember for sure anymore but I think it was about two days and he found the motor. He was so excited! He brought it up and spent a few weeks cleaning it up. He said it was in good shape because it had been at the bottom in fresh water with very little oxygen. When it was ready, it ran like a champ and became my motor! I used it on the back of our wooden, home-made canoe which had a flat transom on the rear. I would pull my younger siblings on waterskis, sleds and disks behind the canoe! That lasted for awhile until they got bigger and heavier and the old motor just couldn't get them up any more. Good times.

Well, now many, many years later, I would like to sell it. I cannot find a model/serial number plate on it anywhere and I have searched all over that engine. Do I need to remove a part of the cover? A cursory search of the internet tells me it may be a model TD20 from the 1940s, but I'm not sure. I would greatly appreciate any help either identifying the motor and/or telling me where I can locate the plate.

What would be a middle-of-the-road, fair price to ask? It's not a thing of great beauty with that big dent in the hood. Still, would someone want it?

Thanks very much in advance for your help!
Carol

I got the cover off and yes indeed, it is a TD-20. I know these were manufactured 1946-49. Is there any way to pin down the exact year via the serial number?

What serial number do you think this is? Is it 669565? I should have made a rubbing/tracing but I already put the cover back on.

How does it look underneath the hood to you? Great? Good? Fair? Or ugh - pretty bad? I know so little about boat engines... I really appreciate any help.