Big Squam Lake, NH's 2nd largest lake:
Rt 93-Exit 24 Ashland to Holderness, on Rt 3/25-west to Rt 113-north for 200-yards to free-to-use, NH Fish & Game boat launch with trailer parking and rest room, next to NH Science Center ..... about 15-minutes drive from Rt 93-Exit 24 going through small towns of Ashland and Holderness .... take a left on Rt 113 just beyond the Holderness Public Library.
The State of NH twin boat launch ramps on Squam unload into the Squam channel which is a 300(?)-yard long river that connects Big and Little Squam Lakes.
A 16-18' boat is like a good size for
www.wikipedia.org/wiki/Squam_Lake ..... or even a 14' aluminum side-steer boat with a 25-hp.