Near the dam there's the Tufts Sailing team boat house where you can launch a bigger boat like a bass boat. I am pretty sure it's open to the public, and I've seen people use it all the time. There's also plenty of parking there as well.
I dont think gas motors are allowed on Upper Mystic. Lower Mystic is ok but you need to launch at the ramp in Medford at the yacht club and drive up the river.
