This problem has to have a solution somewhere. There as so many moorings I can see from where I work, that never have a boat on them all summer. I mean, at least ten, that are unused. The problem is that this is a 37 foot boat and the current in many places in Portsmouth, is over 4 knots. The mooring for a 37 foot boat would have to be robust. I grabbed an unused mooring a few years ago, just for a night, and never thought a thing of it, but that was one night, a 25 foot boat, and on the Maine side of the river. The New Hampshire side may be more closely monitored. I could probably find a mooring for a smaller boat, but anything I could find in a week or two would be hopelessly undersized for 37 feet. Big difference between a 7000# boat and a 17000# boat..... Did you try Great Bay Marina ?
"Ulysses" - Alfred Tennyson