First off; check ActiveCaptain for a listing of ALL marinas.
I live in MA, but keep my boat in RI for 2 reasons; 1-Narragansett Bay (for the admiral) is protected and great sailing. 2- NO tax on Boats. Rhode Island has a strong maritime heritage, and strives to keep it alive, by having no taxes on boats. MA will hit you for sales tax/use tax, excise tax, and anything else that the pinheads in Boston can think of.
If you wish to keep it in MA, Cottage Park, and Constitution Marina are two popular ones, as well as the Winthrop Yacht Club. You could also check with Mark Healy, owner of the Boston Harbor Sailing Club Boston Harbor Sailing Club - Sailboat Racing Moorings Rentals Charters
, as he has about 10 moorings that he will lease for the summer.
Good luck, and let us know where you land.