There are two spots you can put in on RT 27 just under the bridge over the Charles River and paddle up stream or you can put in off West St next to the bridge over the Charles and paddle down stream. I scouted thease out last week but that was before it started to rain in any case it is a short drive if one looks bad.

http://www.bostonkayaker.com/publishmap/charlesmedfieldwestpublishpdf.pdf