Hi Alex, here is a ditty I wrote the other day about Westport Harbor, our summer base back in the day, and environs.
Trawler Forum - View Single Post - Anchorages - or open mooring fields - southern NE
We day tripped Narragansett Bay several times, so I won't hold out total expertise on harbors and marinas there.
Heading up the Sakonnet, around the corner from Westport, you sometimes can get a transient spot in little Sakonnet Point harbor. Charming, but not a lot there, but at one point they were going to offer access to the nice Sakonnet Point Club there. You could call the club or harbormaster:
Sakonnet Point Marina
Sakonnet Point Club - Boating
Further up the river comes Tiverton, with some moorings and dockage on town (east side) and a larger full service marina on the west side of the river.
Continue up the river to Fall River and Battleship Cove in downtown Fall River. Definitely a fun stop.
The Waterway guide Northern edition does a good job of covering this whole area. What are your objectives?