Great points, Minnewaska.
To the other chap talking about a lien being filed on the boat... couldn't this be cleared up with the county with your bill of sale or title showing your date of purchase? Granted, nobody wants any kind of lien on their property, but there wasn't a lien on the boat when he bought it. The tax and any penalties for tardy payment should fall squarely on the previous owner.
Poster, was there a lien on the boat for these taxes when you bought the boat?