I'm still not sure whether the boat has a Coast Guard documentation number or not. If so, use this link http://www.st.nmfs.noaa.gov/st1/Coas...selByName.html
to track the boat history down either by the doc. number or by the name. Otherwise, not sure how to track down the history based on HIN. Maybe someone else here can give you a lead on that?
BTW, it does sound to me like the guy is up to something. You haven't mentioned price, but banks track large cash transactions and report them to the feds.