N.H. Rev. Stat. Ann. § 270:121

No person shall use or operate any powerboat in excess of 40 miles per hour 1/2 hour before sunrise to 1/2 hour after sunset or in excess of headway speed from dusk to dawn on the Piscataquog River in the town of Goffstown and the city of Manchester. Any person who violates the provisions of this section shall be guilty of a violation.