Abstract: A marine engine exhaust system is provided that utilizes a single catalyst housing through which exhaust gases from multiple heads of an exhaust system flow. A first conduit directs a first exhaust gas from a first engine head or exhaust manifold to the catalyst, and a second conduit directs a second exhaust gas from a second engine head or exhaust manifold to the catalyst. The first and second conduits may be separate or may merge prior to the catalyst. The catalyst includes a housing and at least one substrate to convert the first and second exhaust gases into processed exhaust gas. A third conduit directs the processed exhaust gas away from the catalyst. At least one pre-sensor may be located upstream of the catalyst housing, and at least one post-sensor may be located downstream of the catalyst housing.

Abstract: A marine engine exhaust system is provided. One exemplary embodiment of the system includes first and second manifolds. A first gas is transferred through a first conduit from the first manifold and is isolated from cooling water through at least a portion of the first conduit. A second conduit is in fluid communication with the second manifold and allows a second gas to be transferred through that is isolated from cooling water through a portion of its length. The first and second conduits are in fluid communication with a third conduit in which the first and second gases merge. Cooling water is merged with either the first or second gas, or both, in the first and second conduits before the first gas and second gas merge in the third conduit.

Abstract: A marine engine exhaust system is provided. The system includes a first and second manifold. A first conduit is in fluid communication with the first manifold so that a first gas is transferred into a first gas passageway of the first conduit. The first conduit has a first cooling fluid passageway. A second conduit is in fluid communication with the second manifold so that a second gas exiting the second manifold is transferred into a second gas passageway of the second conduit. The second conduit has a second cooling fluid passageway. Cooling fluid is transferred through the first cooling fluid passageway so as to have a direction of flow through the first conduit opposite to the direction of flow of the first gas through the first gas passageway of the first conduit.

Abstract: A marine engine exhaust system is provided. The system includes a first and second manifold. A first conduit is in fluid communication with the first manifold so that a first gas is transferred into a first gas passageway of the first conduit. The first conduit has a first cooling fluid passageway. A second conduit is in fluid communication with the second manifold so that a second gas exiting the second manifold is transferred into a second gas passageway of the second conduit. The second conduit has a second cooling fluid passageway. Cooling fluid is transferred through the first cooling fluid passageway so as to have a direction of flow through the first conduit opposite to the direction of flow of the first gas through the first gas passageway of the first conduit.

Abstract: A marine engine exhaust system is provided. One exemplary embodiment of the system includes first and second manifolds. A first gas is transferred through a first conduit from the first manifold and is isolated from cooling water through at least a portion of the first conduit. A second conduit is in fluid communication with the second manifold and allows a second gas to be transferred through that is isolated from cooling water through a portion of its length. The first and second conduits are in fluid communication with a third conduit in which the first and second gases merge. Cooling water is merged with either the first or second gas, or both, in the first and second conduits before the first gas and second gas merge in the third conduit.