I found the HIN on the boat. It's completely different. I plan to contact him, just wanted to get my ducks in a row first. The seller seemed pretty shrewd and careful, said the boat has been in his family since new. My best guess is that he gave me the wrong title on purpose for some reason, like he does not have the correct one, and knows that I can take this title in and get a tag anyway. He answered questions about the boat via text message after I bought it, so he wasn't trying to dodge me completely. It's mysterious. I wondered if someone had heard the same story and had a guess about what's going on.
We were texting back and forth and I left a message waiting for a response. In the mean time my phone broke. I think the best thing is to try to talk face to face about it. I'll certainly give him a chance to straighten it out.
I can't call or text from my phone right now because I dropped it in the lake when I finally found the HIN (Placed the phone carefully inside the boat before crawling on the pontoon. But it was on a compartment cover that flipped open and dumped me and the phone in the lake as I climbed down. If I had left my phone in my pocket all would have been ok.)
If I had seen any discrepancy like airshot did, I would have left. There are a lot of boats out there.