Cool,
Green Harbor has a great ramp.
Study your chart, find and circle Farnham Rock, this baby feeds on outdrives/outboards.
Unless your boat is light, the best way to duxbury bay is from green harbor, go south 5 miles and around the gurnet, their town ramp is very gradual and like mentioned you have to disconnect your trailer to park
They bays are shallow so know where you are, it's a long time between tides
.
Good Luck, Marshfield is very nice.