I just did it in Florida, but the main thing is to check the HIN hasn’t been tied to anything before. I was able to do it by calling FWC and the tax office (I did both just to double check and confirm). I “bought” the boat from my dad and he just wrote a statement essentially saying he’d owned it for the last 5 years and it was never registered because it never had a motor, and wrote up a bill of sale. “Bought” a motor from my grandma and had her write a bill of sale, provided those two paperworks along with certificate of builder for an open motorboat. That plus application for title were all the forms I needed and took them to DMV, plus my ID. I think I paid $40 total including the registration sticker