Here is Georgia's requirements.
Boat title: bill of sale with former owners name, signature, address, HID.
If current and from same state, just send in the previous owners registration card and filled out transfer and renewal slip in your name and address with appropiate amount of money.
Out of state or new: bill of sale and application for new registration (new to this state or new).
No HID number, salvaged or homemade: apply for inspection by DNR, if approved they will affix HID number.
No bill of sale, no registration possible.
Trailers must have mfrs number and bill of sale and be checked by nearest police station annex (that actually does inspections). Then go to tag office for tag registration. Homemade trailers must apply for state issued homemade trailer number then do all of the above, except bill of sale.
Outboard motors: They don't care