from the county code
http://www.co.kittitas.wa.us/boc/countycode/title09.aspx#Chapter_9.16MOTOR BOATS PROHIBITED ON COOPER LAKE
Sections
9.16.010 Violation.
9.16.020 Motor boat defined.
9.16.010 Violation.
It is unlawful and a violation of this chapter to operate any motor driven boat, vessel or aircraft of any type on Cooper Lake located in Township 22 North, Range 13 East, Kittitas County, Washington. (Ord. 2011-02, 2011; Ord. 99-09, 1999; Ord. 63-1 § 1, Vol. M, p. 517, 1963).
9.16.020 Motor driven boats and vessels defined.
For the purpose of this chapter "Motor driven boats and vessels" are defined as all boats and vessels which are self-propelled by a motor. This does not include boats or vessels that are driven by wind energy or human effort. "Vessel" includes every description of watercraft on the water, other than a seaplane, used or capable of being used as a means of transportation on the water. However, it does not include inner tubes, air mattresses, sailboards, small rafts, flotation devices or toys customarily used by swimmers. (Ord. 2011-02, 2011; Ord. 99-09, 1999; Ord. 63-1 § 2, Vol. M, p. 517, 1963).