Abstract: A marine engine exhaust system includes a catalyst arranged to intercept a flow of exhaust flowing along the exhaust system, a water muffler downstream of the catalyst, and a water-activated exhaust valve disposed between the water muffler and an upstream catalyst and configured to impede flow of water upstream from the muffler to the catalyst.

Abstract: An exhaust manifold cooling jacket has internal passages for the circulation of liquid coolant and encloses an exhaust manifold such that a gap is created between the exhaust manifold and cooling jacket. Flowing coolant through the jacket regulates outer jacket temperature while enabling high intra-manifold exhaust gas temperatures for thorough intra-manifold combustion and improved emissions. A liquid-cooled exhaust system includes a turbocharger disposed between manifold and elbow, with liquid-cooled coolant flowing from manifold to elbow through the turbocharger. Another liquid-coolant exhaust manifold contains an internal exhaust combustion catalyst wrapped in an insulating blanket. In some marine applications, seawater or fresh water coolant is discharged into the exhaust gas stream at an attached exhaust elbow.

Abstract: An exhaust manifold cooling jacket has internal passages for the circulation of liquid coolant and encloses an exhaust manifold such that a gap is created between the exhaust manifold and cooling jacket. Flowing coolant through the jacket regulates outer jacket temperature while enabling high intra-manifold exhaust gas temperatures for thorough intra-manifold combustion and improved emissions. In some applications, a liquid-cooled exhaust system includes a turbocharger disposed between manifold and elbow, with liquid coolant flowing from manifold to elbow through the turbocharger. Another liquid-cooled exhaust manifold contains an internal exhaust combustion catalyst wrapped in an insulating blanket. In some marine applications, seawater or fresh water coolant is discharged into the exhaust gas stream at an attached exhaust elbow.

Abstract: A method of controlling emissions from an internal combustion engine including governing engine speed with respect to a constant speed, maintaining an air/fuel ratio of the engine, flowing exhaust from the engine through an exhaust system containing a catalyst, monitoring a variable with a feedback sensor located upstream of the catalyst, and controlling the air/fuel ratio of the engine as a function of the variable. In one application, the engine is configured for marine applications, including electric power generation and propulsion.