An exhaust conduit for a marine exhaust system includes an inlet end portion connectable to an exhaust manifold, an outlet end portion that directs exhaust gases toward an exhaust system outlet, a catalytic converter assembly arranged between the inlet and outlet end portions, and inner and outer tubes. The inner tube directs exhaust gases from the exhaust manifold to the catalytic converter assembly, and the outer tube surrounds the inner tube to define a cooling liquid passage between the inner and outer tubes. A flange is secured to the inner and outer tubes at inlet ends thereof, the flange being connectable to an outlet of the exhaust manifold. The inner tube has a uniform diameter between the flange and the catalytic converter assembly, and is welded to the flange independently of the outer tube. First and second welds join the inner and outer tubes to the flange at radially inner and outer faces, respectively, of a flange rim.

An exhaust muffler for a marine exhaust system includes an inner conduit, an outer conduit surrounding the inner conduit and a plurality of spiral baffles extending radially outward from the inner conduit to the outer conduit. The outer conduit has end portions connectable to exhaust conduits for directing a mixture of fluid and exhaust gas towards an exhaust system outlet. The mixture flows through the inner conduit and through a cooling passage between the conduits. One or more of the spiral baffles has multiple openings for improving the mixing process of exhaust gas and fluid.

An engine includes an exhaust sensor projecting from an opening in an inner surface of a first exhaust pipe to inside of an exhaust passage, and a projection provided in the inner surface of the first exhaust pipe along the opening, and positioned farther inside the exhaust passage than the opening, wherein at least a portion of the projection is positioned upstream of the opening in a flow direction of exhaust gases.

An exhaust conduit for a marine exhaust system includes an inlet end portion connectable to an exhaust manifold, an outlet end portion that directs exhaust gases toward an exhaust system outlet, a catalytic converter assembly arranged between the inlet and outlet end portions, and inner and outer tubes. The inner tube directs exhaust gases from the exhaust manifold to the catalytic converter assembly, and the outer tube surrounds the inner tube to define a cooling liquid passage between the inner and outer tubes. A flange is secured to the inner and outer tubes at inlet ends thereof, the flange being connectable to an outlet of the exhaust manifold. The inner tube has a uniform diameter between the flange and the catalytic converter assembly, and is welded to the flange independently of the outer tube. First and second welds join the inner and outer tubes to the flange at radially inner and outer faces, respectively, of a flange rim.

An exhaust system is for a marine propulsion device having an internal combustion engine. A catalyst housing has a housing inlet end that receives an exhaust gas flow from the internal combustion engine into the catalyst housing and an opposite, housing outlet end that discharges the exhaust flow out of the catalyst housing. A catalyst is disposed in the catalyst housing. The catalyst has a catalyst inlet end that receives the exhaust gas flow and an opposite, catalyst outlet end that discharges the exhaust gas flow. A catalyst mantel is on an outer periphery of the catalyst. The catalyst mantel has a mantel inlet end and an opposite, mantel outlet end. A radial flange is on at least one of the mantel outlet end and mantel inlet end. A connector mates with an inner diameter of the catalyst housing. The radially extending flange of the catalyst mantel is axially sandwiched between the connector and a radially inner shoulder of the catalyst housing.

An internal combustion engine for an outboard motor comprises a cylinder block having first and second banks of cylinders that extend transversely with respect to each other in a V-shape so as to define a valley there between. An exhaust manifold conveys exhaust gas from the internal combustion engine and is at least partially disposed in the valley. A supporting mechanism supports the exhaust conduit with respect to the internal combustion engine. The supporting mechanism is configured to allow the exhaust conduit to move with respect to the internal combustion engine in 360 degrees in a plane defined by the lateral and transverse axes, and laterally towards and away from the internal combustion engine, thereby facilitating assembly of the exhaust manifold and the internal combustion engine despite positional tolerance differences there between.

A method for operating a boosted internal combustion engine is provided. The engine includes a first cylinder in a first cylinder group and a second cylinder in a second cylinder group, each of the first and second cylinders having two activatable outlet openings adjoined by an exhaust line, one of the outlet openings of each of the first and second cylinders coupled to a first turbocharger including a first turbine and one of the outlet openings of each of the cylinders coupled to a second turbocharger including a second turbine, the method comprising: if engine load is less than a threshold load value implementing a first operating mode that includes deactivating the second cylinder, deactivating one of the activatable outlet openings in the first cylinder, and activating one of the activatable outlet opening in the first cylinder.

A method is disclosed for optimizing fuel economy during an engine warm up phase of operation of an internal combustion engine. An exhaust manifold may have a coolant jacket through which a coolant may flow. A temperature of the coolant in the exhaust manifold may be determined to detect when it is at a predetermined maximum threshold, which represents a temperature threshold just below a temperature at which the coolant will begin to boil. When this threshold is reached, then a determination may be made as to a minimum rate of flow of the coolant through the exhaust manifold which maintains the coolant at about the predetermined maximum threshold, and the coolant may be flowed through the exhaust manifold at the determined minimum rate of flow.

Methods and systems are provided for a 2-port integrated exhaust manifold for an inline-3, inline-6, V-6, and/or V-12 engine. In one example, a system may include an exhaust manifold integrated within a cylinder head of an engine block. The integrated exhaust manifold may include a first set of two runners from a first outer cylinder coupled to a first manifold exhaust port, a second set of two runners of a second outer cylinder coupled to a second manifold exhaust port, and one runner of an inner cylinder coupled to the first manifold exhaust port and another runner of the inner cylinder coupled to the second manifold exhaust port.

A modular exhaust manifold includes a plurality of exhaust manifold segments coupled together along a common axis. Exhaust manifold segments include a water jacket tube defining a liquid coolant passage around each of the plurality of exhaust manifold segments. The internal combustion engine also includes a coupling assembly for joining adjacent exhaust manifold segments. The coupling assembly includes a plurality of annular sealing devices configured to fit within a first set of grooves formed on an end portion of a first exhaust manifold segment. The coupling assembly also includes a spacing collar configured to attach to the end portion of the first exhaust manifold segment and couple with a fixed radial flange formed on an adjacent end portion of a second exhaust manifold segment to join the first exhaust manifold segment and the second exhaust manifold segment.