Exhaust control device for water jet propulsion boat

Abstract

A watercraft has an exhaust conduit that includes an exhaust gas passage and a cooling water passage. The exhaust gas passage and the cooling water passage are configured to mix together an exhaust gas flow and a cooling water flow at a junction. The mixture is ultimately discharged from the watercraft. The watercraft has an exhaust valve drive system that has a drive motor and a controller. The exhaust valve drive system operates an exhaust control valve to control the flow of exhaust gases through the exhaust conduit. The exhaust control valve includes a pivot shaft extending generally horizontally and attached to a valve body. The exhaust control valve is positioned upstream of the junction. The controller operates the drive motor which drives the exhaust control valve between an open position and closed position. The controller can receive signals from an engine rotation sensor and a throttle opening sensor and can control the drive motor based on these signals. A catalyst for treating the exhaust gases is disposed upstream in the exhaust gas passage along the exhaust control valve.