US Patent 7699675 Marine exhaust elbow with condensation reducing water circulation system

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.