Hi, There is an information tag shown on the side of the outboard… a better picture of that would help. It appears to indicate that it is a KB1A. If it is the it is a 1941 Mercury 3.1hp outboard. It is a common but collectable motor. People collect these Mercs but not a high value engine. It looks to be missing some lower engine covers. The covers are usually missing. Post an ad in classified section and I’m sure someone would make you a reasonable offer.
Actually your motor looks pretty complete to me. One question that will go a long way to determining value is if the motor is frozen/seized up? If you pull on the rope, does the motor turn over and spin the prop?