Idle speed control valve control system

An engine for a watercraft comprising a cylinder body, at least one cylinder bore being formed in the cylinder body, a piston being mounted for reciprocation within the cylinder bore, a cylinder head being disposed over a first end of the cylinder bore, a crankcase member being disposed over a second end of the cylinder bore, an output shaft being disposed at least partially within a crankcase chamber at least partially defined by the crankcase member, the output shaft powering an output device, a combustion chamber being defined at least partially within the cylinder bore between the cylinder head and the piston, an intake conduit communicating with the combustion chamber, a throttle valve being disposed within the intake conduit, a throttle valve sensor being capable of sensing a position of the throttle valve, a bypass passage communicating with the intake conduit at a location between the throttle valve and the combustion chamber, an idle speed control valve being disposed along the bypass passage, a speed sensor capable of deducing a traveling speed of the watercraft, a controller electrically communicating with the idle speed control valve, the speed sensor and the throttle valve sensor, the controller being adapted to close the idle speed control valve at a first rate when the watercraft is traveling at a speed greater than a preset value and the throttle valve is rapidly closed and to close the idle speed control valve at a second rate when the watercraft is traveling below the preset value and the throttle valve is rapidly closed.