The problem with this idea is that some states require that your register your boat there, assuming that their state is the location of "principle use" in as little as 90 days of presence. So, theoretically, if you stay three month in one such state in a year, you need to register it in that state, with the associated fees, annual use tax, etc, then move on to the next state that has a "90 day requirement", you need to register it again in THAT stated, then the next, etc. Each "registration" comes with the requirement to pay for a full year of taxes. So, once again, theoretically, since there are 4 "90 day periods" plus a few extra days in any given year, you may be legally required to re-register your boat up to 4 times in the same year, just to fulfill the local requirements. Granted, it is unlikely the timing would require that number of re-registers, but say you boating primarily in two adjacent states that have the 90 day requirement: When you move from State A to State B, you register in your new State B. State A's registration becomes null and void. If you move across the line back into State A, you need to register AGAIN back in State A . . . .
I wish they would just come up with a National registration (wait, they already HAVE that, it's called Federal Documentation!) . . . . but it's all about revenue, not keeping track of the boat . . . .
People have reported here on Trawler Forum that they have received dunning notices from States where they were just passing through. Threatening to put a lien on their boat if they don't pay up, or PROVE that they weren't in that state for longer than whatever their prescribed time is. So the burden of proof is on you, the boat owner to prove that you did NOT break the law! Difficult if you didn't happen to purchase fuel, or stay at a marina in an adjoining state during the period under discussion. Some states just send out blanket registration notices to all boats present where the enforcement officer happened to take a walk one day.
Okay, off my soapbox for now . . . .