There shall be a Town Administrator appointed by the Board of Selectmen for a period not to exceed 3 years; the Town Administrator shall be eligible for reappointment in accordance with M.G.L ch. 41, § 23A. The Town Administrator shall be responsible to the Board of Selectmen, and as chief administrative officer of the Town shall have general administrative authority over all departments and officials appointed by the Board of Selectmen except for the Police and Fire Departments.