Stern drive arrangements having idle relief exhaust gas bypass

A stern drive arrangement for propelling a marine vessel in water, the stern drive arrangement comprising an internal combustion engine;

• a lower gearcase that supports a propulsor that is operably connected to the internal combustion engine;
• an exhaust manifold configured to convey exhaust gas from the internal combustion engine;
• a primary exhaust conduit configured to convey the exhaust gas from the exhaust manifold to an underwater outlet on the propulsor;
• a secondary exhaust conduit configured to convey the exhaust gas from the exhaust manifold to an above-water outlet on one of the marine vessel and the stern drive arrangement;
• a diverter valve that is movable into and between an open position in which the exhaust gas is allowed to flow through the secondary exhaust conduit to the above-water outlet and a closed position in which the exhaust gas is at least partially prevented from flowing through the secondary exhaust conduit to the above-water outlet;
• and a bypass conduit configured such that the exhaust gas in the secondary exhaust conduit can bypass the diverter valve and discharge to atmosphere when the diverter valve is in the closed position, thereby reducing exhaust noise emanating from the above-water outlet and reducing exhaust gas discharged through the underwater outlet when the internal combustion engine is operated at idle speed.

A stern drive arrangement for propelling a marine vessel, the stern drive arrangement comprising an internal combustion engine;

• an exhaust manifold that conveys exhaust gas from the internal combustion engine;
• a primary exhaust conduit configured to convey the exhaust gas from the exhaust manifold to an underwater outlet on the stern drive arrangement;
• a secondary exhaust conduit configured to convey the exhaust gas from the exhaust manifold to an above-water outlet on the marine vessel;
• a diverter valve that is movable into and between an open position in which the exhaust gas is allowed to flow through the secondary exhaust conduit and a closed position in which the exhaust gas is at least partially prevented from flowing through the secondary exhaust conduit;
• a bypass conduit through which the exhaust gas in the secondary exhaust conduit can bypass the diverter valve and discharge to atmosphere when the diverter valve is in the closed position, thereby reducing exhaust noise emanating from the above-water outlet and reducing exhaust gas discharged through the underwater outlet when the internal combustion engine is operated at idle speed;
• and a computer controller configured to control a position of the diverter valve.