Sooo...state gets the tax on a new boat purchase and AGAIN gets the tax when you buy a previously new (and taxed) boat? Am I missing something?
The only exception I can think of is if you trade in the used boat when purchasing another one. Same applies to cars & trucks. Doesn't matter if you're buying a new or used vessel/vehicle - the trade-in value offsets the new(er) purchase and you only pay sales tax on the net price.
But in general yeah, the state collects sales tax on the sale or resale of a boat.
"Decency is not news; it is buried in the obituaries --but it is a force stronger than crime" ~ Robert A. Heinlein, 1952
I can't give legal advice yet, but this site may have some of the answers you need: https://texaslawhelp.org/