The Georgia boat registration process has changed over the years to require bill of sale, affidavit, notary public when transfer/sale of a boat. A rebuilt/derelict or even homemade boat has a whole nuther can of worms to go through which includes an anal probe from the Coast Guard on both you and the boat.
If the boat is in his name you are most likely gonna have to contact him and get it transferred with the appropriate paperwork.
Here are some links.
http://georgiawildlife.dnr.state.ga....n_boating.aspx
Also look at the bottom of the page at Boat Registration Database, search it to be sure it is his boat.