You mean registering( or in some states titling), as opposed to licensing. I have to assume it’s the sales tax you are tying to avoid, not the actual registration fee.
anyone can register their boat in Delaware, and they won’t owe DE any sales tax. but if you are keeping your boat all year in one other state, it won’t do you much good.
havent seen in lately, but back in early 2000’s the tax agents in Jersey and MD used to walk the docks of the bigger marinas, take note of all the boats without the state sticker. Head to the office, pull the slip contracts. If a slip holder had an annual contract in NJ ( for example), and no NJ sticker on the boat, you owed not only the tax, but the penalty too. If you could prove your boat was not in NJ for a majority of the year, depsite the fact you had the annual slip - you certainly could win. And if it was a seasonal slip, and you had paperwork for winter storage in another state, or Lived in another state, you were ok. That’s what I always did back then. Registered my boat in DE, used it mostly in Maryland and NJ, and kept it over the winter in PA. hardly ever saw DE water or land - but NJ and PA and MD couldn’t tax me - as I wasn’t in waters of any of those state for more than a few months.
But really there is no free lunch - if you are keeping your boat in some state that charges taxes - hard to get much benefit of a DE registration, without being very creative, or moving amongst states every year. Creative would be to buy the boat, register it in DE, and then before you berth it in your home state - sell it to your wife for one dollar. Now you only owe tax on the purchase price, right?