Image Number 3 for United States Patent #5106330.
The invention provides a marine propulsion device comprising a powerhead including an exhaust gas discharge port, a gearcase rotatably supporting a propeller shaft connected to the powerhead and including an exhaust gas discharge, and a lower unit including an upper portion supporting the powerhead and a lower portion connected to the gearcase, with the lower unit comprising an inner exhaust housing having a generally vertical wall, an open top in communication with the powerhead exhaust gas discharge port, a bottom having therein a first exhaust gas outlet and a second exhaust gas outlet at the top portion of the wall, and an outer exhaust housing also having a generally vertical wall in surrounding relation to the inner exhaust gas housing and defining a vertically extending generally annular space between the inner and outer exhaust gas housings, the space communicating with the second exhaust gas outlet. A water pump, driven by the powerhead, supplies water to the powerhead and to the space between the inner and outer exhaust gas housings. A means for varying the water in the space between the inner and outer exhaust gas housings between a first lower level and a second upper level responds to an operating condition in the powerhead, and an idle exhaust gas discharge means operates only when the water in the annular space between the inner exhaust housing and the outer gas housing is at the first lower level.
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