(1) The Clark Fork River and its tributaries, unless specified elsewhere in this chapter, are closed to all motorized watercraft, including personal watercraft as defined in 23-2-502, MCA, except:

(a) from Kelly Island (Spurgin Road) Fishing Access Site boat ramp and the Grass Valley Ditch Diversion to Harper's Bridge Fishing Access Site:

(i) any motorized watercraft, except personal watercraft as defined in 23-2-502, MCA, are permitted from May 1 to June 15; and

(ii) any motorized watercraft 20 horsepower or less are permitted from October 1 through January 31.

(b) from Harper's Bridge Fishing Access Site to St. John's Fishing Access Site:

(i) any motorized watercraft, except personal watercraft as defined in 23-2-502, MCA, are permitted from October 1 to June 15; and

(ii) any motorized watercraft 20 horsepower or less are permitted from June 16 through September 30.

(c) from the mouth of Fish Creek to the Montana border.