I'll toss out one more thread as another one with some helpful info for that area:
NOTE: In that thread I discouraged DrB from considering Green Harbor (Marshfield), but with your boat I think it would be fine. If you were making good progress and didn't want to stop at Scituate, you could press on to GH for the night. You can get provisions at the Brant Rock Market, or walk a bit farther and have a FABULOUS breakfast at Arthur and Pat's restaurant (across the street from the old WWII submarine watch tower).
I'll also echo the sentiment that going into Plymouth/Duxbury would be a detour. P/D is a better stopover if you're heading to or from the canal, but you still need to time the tides right.