An exhaust manifold is for an internal combustion engine on an outboard marine engine that is configured to power a propulsor to provide a thrust in a longitudinal direction. The exhaust manifold comprises an exhaust runner that transversely and longitudinally rearwardly conveys the exhaust gas from the internal combustion engine, an exhaust log that vertically upwardly conveys the exhaust gas from the exhaust runner, and an exhaust elbow that conveys the exhaust gas from the exhaust log vertically upwardly, longitudinally forwardly, and then vertically downwardly.

The cooling device for a power source for a ship propulsion device that pumps up cooling water, from which foreign matters with sizes that cause clogging of a cooling water route have been removed, supplies the cooling water to a cooling water passage (30), and discharges the cooling water to outside after cooling a power source (10) includes: a cartridge-type filtration device (40, 73) that is provided at a midpoint of a first water passage (36, 71) in the cooling water route and incorporates a filter (45, 46) for filtrating foreign matters remaining in the cooling water; and a second water passage (38, 72) that is branched from the first water passage and adapted such that a valve member (53) is opened to cause the cooling water to flow in a case in which clogging occurs in the filter.

An outboard motor catalytic converter that can downsize an outboard motor by making a space, where catalysts are installed, small and can ensure efficient reaction of the catalysts. The outboard motor catalytic converter includes exhaust pipes that are connected to exhaust manifolds of an engine of the outboard motor. Catalysts are installed inside the exhaust pipes, and at least a portion of each of the exhaust pipes, which corresponds to a place where the catalysts are installed, is formed to have a double structure constituted of an inner pipe and an outer pipe.

An exhaust pipe has an upstream-side exhaust pipe extending downward from an engine to house a catalyst for exhaust gas purification, and a downstream-side exhaust pipe located downstream of the upstream-side exhaust pipe, and extending upward from the catalyst and then bending downward. Under a configuration in which an exhaust pipe is disposed below an engine, with a simple configuration, a catalyst is hardly exposed to water.

Constraints on arrangement of catalysts are reduced, and early activation and long-term performance maintenance of the catalysts are both achieved. An exhaust pipe includes a first catalyst provided in a first exhaust pipe extending upward on the side of an exhaust manifold, and a second catalyst provided in a second exhaust pipe that extends downward from a bent pipe extending from the first exhaust pipe and that is adjacent to the first exhaust pipe. The second catalyst is disposed at a position offset to a higher location from an up-down middle position of the first exhaust pipe.

An exhaust gas purification structure of an outboard motor includes an exhaust gas pipe that has an exhaust gas passage through which exhaust gas of an engine can flow; and a catalyst that is provided in the exhaust gas passage and purifies the exhaust gas by allowing the exhaust gas to pass through the inside thereof. The exhaust gas pipe includes a coolant flow passage allowing a coolant that cools the exhaust gas to flow therethrough. An exhaust gas bypass passage allowing the exhaust gas to flow without passing through the catalyst is formed between the catalyst and an inner surface of the exhaust gas pipe forming the exhaust gas passage.

This oil case of an outboard motor is provided below an engine and stores lubricating oil of the engine. In this method for manufacturing the oil case, the oil case is manufactured so as to comprise: an oil chamber; an introduction path that guides upward cooling supply water drawn in from outside the outboard motor; a delivery path that guides downward cooling discharge water that has cooled the engine; a main exhaust path that guides exhaust gas of the engine downward; and a sub exhaust path that guides exhaust gas during low-speed rotation of the engine. The oil chamber, the introduction path, the delivery path, the main exhaust path and the sub exhaust path form an integral structure.

An air intake and exhaust system for a marine engine having an intake manifold and an exhaust manifold includes an air compressor configured to compress ambient air into compressed air and a catalytic converter assembly configured to convert pollutants in an exhaust gas stream received from the exhaust manifold. The air compressor is configured to be fluidly coupled to the intake manifold of the engine for directing at least a first portion of the compressed air to the intake manifold of the engine. The air compressor is also selectively fluidly coupled to the catalytic converter assembly for selectively directing a second portion of the compressed air into the exhaust gas stream at a secondary air injection location at or upstream of the catalytic converter assembly.

A cooling structure for an outboard motor comprises an oil case which has an oil chamber for storing lubricant oil for an engine. Said cooling structure further comprises: a main exhaust gas passage which guides exhaust gas to a lower side; a cooling water outbound path which guides cooling supply water taken from outside the outboard motor to an upper side, and cools the periphery of the main exhaust gas passage in the oil case by means of the cooling supply water; a cooling water inbound path which guides cooling discharge water that has cooled the engine to the lower side and cools the oil chamber by means of said cooling discharge water; and a mixed fluid passage which, on a side below the oil case, cools the exhaust gas by mixing the exhaust gas and the cooling discharge water.

A marine drive has a primary exhaust outlet on its lower gearcase that discharges a primary flow of exhaust gas from the engine to seawater in which the marine drive is situated. A secondary exhaust outlet is located on the marine drive above the primary exhaust outlet and discharges a secondary flow of exhaust gas from the engine to atmosphere around the marine drive at least when the engine is operated at an idle speed. A tertiary exhaust outlet is located on the marine drive between the primary and secondary exhaust outlets, and discharges a tertiary flow of exhaust gas from the engine to the seawater or to the atmosphere depending upon a current location of the tertiary exhaust outlet with respect to the seawater. A muffler is configured to reduce noise emanating from the tertiary exhaust outlet.