Going through the same thing with my Alumacraft. Not sure how old it is, but it's from the days before they had hull IDs. I'm in Indiana and the BMV are being real jerks about all this. I sent in a pack of forms including a checklist that I carefully ran down to ensure I didn't miss anything. I got it back a few days ago saying I had omitted another damned form. They did supply it at least, so filled it out and sent it back in with a letter explaining I was trying hard to obey the laws of the state, but they sure weren't making it easy.
The only no. on my boat is on the transom brace too. If I had not seen a picture I'd have never found it as it was covered with paint. A little sanding revealed: F 11711
I tried registering it using that no. and they said no dice, that is NOT a hull no. So now going through a long drawn out procedure to basically just allow me to give the state some of my money! You know if this were a 50' cruiser I could maybe understand the red tape, but this is basically a row boat AND I had to send them a picture of it, so no doubt this is not some nefarious scheme to steal an expensive boat.
I contacted AlumaCraft but they ignored my request for a model year. If anybody could tell me how old mine is I'd be grateful.
OK sorry about the rant. Hopefully the original poster had better luck where he's at. All this just to legally put a motor on the back.....sheesh.