Redstripe, if you don't CHECK WITH THE STATES you are going to wind up paying a lot of money or losing your boat to a tax seizure. Simple enough?
The laws are different in eveyr state. In some states you can keep the boat "in the state" while in others it is "in the navigable waters of the state" for a period of "ninety consecutive days" or "30 days" or "no more than 185 days" in one year, and then it has to be registered AS A MOTOR VEHICLE or AS A BOAT or EXEMPTED AS AN ANTIQUE or NOT REGISTERED IF THERES NO ENGINE.
Every one of those variations applies in different states and that's just the beginning. Either visit the state web sites or call their boating authorities and find out the laws. "Some guy on the internet told me" isn't going to scare the tax men away or get you forgiven for not paying their tithe.