You have the 1952 Mercury made Wizard super twin. It is 6 hp and the parts manual is uploaded in the forum. Just search wg-4 and also WG4 in the search box to get information from previous posts.
They are good motors.
At many AOMCI meets they sell for between $100 and $200. So much depend on what buyers are there on a given day. I suggest that you watch www.ebaymotors.com and see if you observe any in similar conditions.