The laws and governing authorities seem to be nothing but trouble. Sometimes you have to work around the law, not with the law.
If the boat has no registration numbers and no identification at all then it is not titled property, so I suppose how to handle the situation would depend on that.
Whatever you do to the boat -- move it, add an anchor or whatever, NOBODY has to know that you did it. Nobody will ever know if you stop by at night and don't tell anybody.
What happens if you come by at night and remove all identification information from it?
Can you find the phone number of the owner and give him a call from a pay phone, anonymously? Tell him that his boat is not properly maintained and is in danger of causing damage to other people's property when the hurricane comes. If he says he won't do anything about it then tell him that you have a friend who needs a boat for a year and he is going to go ahead and start using it
. What I just said was a common sense approach to handling the problem, not a legal approach.
REALLY, wouldn't using the boat be a whole lot better idea than taking it out and sinking it!!! If you use it make sure anything that would identify it to the previous owner is removed during the time that you use it. Then you can call the guy who owns it from a pay phone when you're done and tell him where you've left it
If were that guy, I would be much happier if someone took the boat and sold it and gave me some of the money instead of just sinking it as some here suggest suggest.
Whatever you do to this boat is going to probably be illegal. So while you're at it, just go ahead and use it for something good.