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.

In an exhaust passage, an exhaust manifold connected to exhaust ports of each cylinder of an engine body and formed to extend vertically is arranged in a side portion of a cylinder head. A secondary air supply system has an intake silencer, a check valve configured to permit only a flow to the exhaust passage side, a secondary air supply control valve configured to control a flow rate of the secondary air, and a secondary air supply passage configured to connect those components to each other and the exhaust passage. The secondary air supply system is arranged in a side portion of a cylinder block placed between a crankcase of the engine body and an assembly of the exhaust manifold and the cylinder head.

A V-type engine in which exhaust pipe arrangement is easily performed and purification of exhaust gas can be performed by a single catalyst. Cylinders where pistons operate are arranged in a V-shape, a crankshaft driven by the driving of the pistons is disposed vertically, exhaust pipes communicating with exhaust openings in the respective banks of a cylinder head are included, rear exhaust pipes in the respective banks are merged outside on a side of the crankshaft, and a catalyst holder that holds a catalyst is provided in a merge portion of the rear exhaust pipes. Since the rear exhaust pipes in the respective banks are merged and the catalyst holder is provided in this merge portion, exhaust gas from each bank can be purified by the single catalyst, so that the number of catalysts installed is reduced to thus be able to reduce manufacturing cost.

An engine for an outboard motor is provided with an engine body, an intake system configured to supply combustion air to the engine body, an exhaust passage formed by connecting the engine body and the middle and lower units thereunder, a catalyst provided in the exhaust passage, and an air pump configured to supply secondary air to the upstream side of the catalyst. The air pump is driven by an electric motor.

A V-type engine, an outboard motor, and a ship capable of restricting exposure of a catalyst to water. The engine includes cylinders where pistons operate are arranged in a V-shape, a crankshaft driven by driving of the pistons is disposed vertically, and exhaust pipes communicating with exhaust openings in the respective banks of a cylinder head and a catalyst holder that holds a catalyst in a merge portion where the exhaust pipes are merged in a site located on an upper side of the banks are included.

An outboard engine assembly has an engine unit including an engine unit housing, an internal combustion engine disposed in the engine unit housing, the engine defining at least one combustion chamber, an exhaust system fluidly communicating with the at least one combustion chamber for supplying exhaust gases from the at least one combustion chamber to an exterior of the outboard engine assembly, a gearcase connected to the engine unit housing, a control module connected to the engine for controlling at least one operating parameter of the outboard engine assembly, and a water sensor disposed at least in part in the exhaust system for detecting presence of water in the exhaust system, the water sensor being in communication with the control module, and a propulsion device operatively connected to the engine.

Disclosed is an outboard motor including an exhaust manifold having a plurality of first openings connected to exhaust ports to form a first passage vertically extending, and an exhaust passage having a second passage extending upward along the exhaust manifold, a third passage that is connected to an upper end portion of the second passage and passes over the exhaust manifold, a fourth passage that is connected to the third passage, turns over to the downside, and then extends downward along the exhaust manifold, so that a lower end portion thereof communicates with a fifth passage provided in the engine holder, the second, third, and fourth passages being arranged in one side of the left-right direction of the cylinder block, wherein the exhaust passage is arranged in a swirling shape, and an exhaust gas cleaning catalyst is installed in a middle portion of the second passage.

A system for cooling an engine of a marine propulsion system having an engine and having a cylinder block. An exhaust manifold that conveys hot exhaust gases from the engine and a pump that pumps water from a body of water are also present in the system. A water jacket surrounding the exhaust manifold conveys water from the pump along at least one stream of water having a cross sectional area for cooling the hot exhaust gases in the exhaust manifold. At least one portion of the water jacket includes at least one converging passageway including a wall of the water jacket that tapers inwardly to reduce the cross-sectional area of the stream of water as the water circulates in the water jacket. The pumped water typically has entrained air in the form of air pockets. The converging passageway reduces the air pockets present in the water to provide even cooling of the manifold.

An exhaust system is for a marine propulsion device having an internal combustion engine. The exhaust system comprises a catalyst housing having a housing inlet end that receives exhaust gas flow from the internal combustion engine and an opposite, housing outlet end that discharges the exhaust gas flow. A catalyst is disposed in the catalyst housing. An outlet collector receives the exhaust gas flow from the catalyst housing. The outlet collector comprises a collector inlet end that is engaged with the housing outlet end. One of the collector inlet end and housing outlet end overlaps with the other of the collector inlet end and housing outlet end at a joint. A seal is disposed at the joint between the collector inlet end and the housing outlet end. The joint is devoid of a cooling water jacket.

A tubular protector provided with a basal end side installed in a casing to cover an oxygen concentration detector has a tubular portion configured to house a detecting portion of the oxygen concentration detector in a bottomed hollow formed by blocking a tip side thereof, and an extension configured to extend from a bottom of the tubular portion to a tip and provided with a plurality of channels each communicating with an inner side of the tubular portion and having an exhaust gas inlet port opened outward in a radial direction.