There are different types of
taxes that are often used interchangeably, but they are not the same, or interchangeable. Different states impose different
taxes. Sales tax, use tax, and property tax. So you need to check with the state (and local county) to know what the costs are.
What is important though, is that these taxes are based on where the boat physically is, not the home port listed on the USCG document. The home port can be any city in the US. You don't have to live there, visit there, and it doesn't even need to have access to navigable
water. It is simply a mark of vanity. A home port in the USVI is not different than a home port anywhere else in the US. The boat is flagged US, and that is all that matters.
If you document the boat with USCG, you do not usually need to title the boat in a state. However, some states will still charge a fee, and can require a sticker to show
fees paid, but cannot require numbers be displayed.
Many states will not issue a title or charge
fees for a USCG documented
boats. Even
California does not title or charge fees for a USCG boat. However, If your boat is in
California on January 1st, then whatever county it is in will assess property taxes the following tax year. Never enter California, never pay property tax. But as I said, it varies by locality, not just state, but at the county level. And while California's
rule is "where was the boat January 1st?" other states have different rules, like "Has the boat been here for x months?"
For *most* purposes, the USCG document is equivalent to a title. If there is ever a lien on the boat, of if there is a question of
ownership in court, the USCG document is not sufficient. You probably want
legal help in that case, but the USCG can also provide an abstract of title which will help document the
legal ownership. Few boat owners ever need it.