Sounds like a scam to me too. I got a couple of those from over seas when i was selling my last truck. Also, my sister got a few of those responses recently from a canadian broker when she was selling her rinker. Her bank advised her against getting involved with these types of deals.
I would steer clear and wait till you get some unsuspicious offers.
btw, when you figure out how many miles are on the boat.....let me know