Abstract: Apparatuses for marine propulsion systems having an internal combustion engine comprise an exhaust conduit conveying exhaust from the internal combustion engine; a cooling jacket on the exhaust conduit; and a cooling passage between the exhaust conduit and the cooling jacket. The cooling passage guides flow of cooling liquid from upstream to downstream towards a location where the cooling liquid is mixed with exhaust in the exhaust conduit. First and second baffles are axially spaced apart and extend transversely with respect to the cooling passage so as to disperse the flow of cooling liquid at the location where the cooling liquid is mixed with the exhaust, thereby reducing reversion of cooling liquid in the exhaust conduit. At least one catalyst and at least one oxygen sensor are disposed in the exhaust conduit. The oxygen sensor is adjacent to and oriented parallel to a downstream face of the catalyst so that exhaust flows perpendicularly across the sensor.

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: A marine propulsion system places an in-line engine at a tilted angle relative to a vertical plane in order to reduce the maximum height requirement space of an engine compartment in a marine vessel. The crankshaft axis of the in-line engine can be located on a vertical vessel symmetry plane or can be offset from it. The crankshaft of the inline engine can be disposed parallel to the vessel symmetry plane, within the vessel symmetry plane, or perpendicular to the vessel symmetry plane.