Abstract: A marine propulsion system has an exhaust conduit conveying exhaust gases from an internal combustion engine. The exhaust conduit has a dry portion and a wet portion located downstream of the dry portion. Cooling fluid enters the exhaust conduit to cool exhaust gases flowing through the wet portion. A bypass conduit is connected to the exhaust conduit and conveys a portion of the cooling fluid away from the dry portion to thereby decrease reversion of cooling fluid into the dry portion.

Abstract: A marine transmission provides first and second drive gears that have first and second driving surfaces in contact with first and second quantities of rheological fluid. First and second driven surfaces of a propeller shaft are also in contact with the rheological fluids within first and second cavities. Torque is transmitted between the drive gears and the propeller shaft through the increase in viscosity of the rheological fluid. A dog clutch can also be provided in order to lock the propeller shaft to the driving one of the first and second drive gears after the rheological fluid is used to spin up the propeller shaft to the appropriate speed.

Abstract: An exhaust system of a marine propulsion device is provided with a bifurcated cooling passage in its elbow structure in order to limit the effect of cold water being disposed in thermal communication with exhaust gas passing through the elbow structure. This thermal communication between a stream of cold water and exhaust gas passing through the elbow structure is minimized in order to reduce the likelihood that water vapor will condense out of the stream of exhaust gas as it passes through the elbow structure. An obstruction, or water dam, is used to bifurcate the coolant chamber within the elbow structure while allowing passage of coolant through the obstruction.