Abstract: A marine engine exhaust system has an exhaust conduit conveying engine exhaust gas from upstream to downstream, a sensor sensing oxygen content of the exhaust gas in the conduit, and a shield located in the conduit. The shield is configured to shield the sensor from deleterious effects of liquid when liquid and exhaust gas is reverted in the exhaust conduit from downstream to upstream.

Abstract: An exhaust system for a marine engine uses an orifice to distribute liquid coolant flow between two alternative and parallel paths. One coolant path passes through a generally horizontal portion of an exhaust elbow and the other coolant path passes through the orifice and directly to a vertical riser of the exhaust elbow. The ratio of flow between the two paths changes as a function of engine speed because of the operation of the orifice which provides increased resistance to flow as a function of increased pressure drop across the orifice. Although coolant liquid continues to flow through both paths at all times, the relative magnitudes of the two parallel flows are changed in response to changes in the coolant flow into the elbow which, in turn, changes as a function of engine speed.

Abstract: A heat exchanger for a marine internal combustion engine is disposed between first and sides of a V-shaped engine configuration. A plurality of tubes and related structure are disposed within a cavity formed as an integral part of an air intake manifold of the engine. A first cooling fluid, such as ethylene glycol, is circulated in thermal communication with outer surfaces of the plurality of tubes within the heat exchanger and a second cooling fluid, such as lake or sea water, is circulated through the internal passages of the plurality of tubes. A conduit is provided within an end portion of the heat exchanger to remove heat from a lubricant, such as oil, of the internal combustion engine.