Can a Tow Service Take My Boat if I Dispute Its Charges?

We ran out of fuel a couple miles away from our marina, and I am now involved in a dispute with the tow company that brought us back to our dock. I agreed to an hourly rate for its services over the radio — but when we got back to the dock, the tow operator asked me to sign a contract that included several hours of travel time to and from his dock in another marina. When I asked for a detailed statement, he got belligerent and refused to discuss or negotiate his fee. He simply demanded payment and said he would come back to take my boat if I did not sign immediately. The next day, he did just that. When I tracked the boat down a couple of days later, it was in dry storage in a boatyard. The tow operator said I owed an additional $1,100 for the tow and that I was responsible to the yard for storage and other fees. The tow operator insists that he has a legal right to take my boat, because I disputed charge and he is exercising his maritime lien rights. That just doesn’t seem right. What can I do?  For...