There are included: a motor contained in a top cover; a vertical shaft that is rotationally driven by the motor, the vertical shaft being contained in an extension casing; and a propeller that is rotationally driven by the vertical shaft, the propeller being provided at a gear casing, wherein a heat exchanging part is provided inside a front portion of the gear casing, and inside the heat exchanging part, there are formed an inflow-side oil channel and an outflow-side oil channel that cooling oil for cooling the motor flows through.

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.

A marine outboard motor for a marine vessel. The marine outboard motor includes: a housing comprising a chamber and at least one inlet arranged to be submerged, in use, into a body of water in which the marine outboard motor is operated, in order to draw water into the chamber; an engine assembly comprising an internal combustion engine; a drive shaft positioned in the housing, wherein the drive shaft is coupled to the internal combustion engine to drive a propulsion arrangement; a cooling system for cooling the internal combustion engine, the cooling system configured convey drawn water along a coolant flow path through the housing to deliver the drawn water to the internal combustion engine; and a sleeve by which the drive shaft is sealed from drawn water within the housing, the sleeve having first and second ends, wherein at least a part of the drive shaft is encased within the sleeve.

An outboard motor includes a first cooling water passage through which first cooling water including water from outside an outboard motor body passes to cool a first cooling target including at least one of an electrical component other than an engine and fuel in a fuel tank, and a first pump that is an electric pump that pumps the first cooling water from outside of the outboard motor body and flows the first cooling water into the first cooling water passage.

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.

A system to control a watercraft including an engine includes a first temperature sensor and a controller. The first temperature sensor is operable to detect a temperature of the engine. The controller is configured or programmed to obtain the temperature of the engine either upon an activation of the controller or a start of the engine. The controller is configured or programmed to estimate an environmental temperature of the watercraft based on the temperature of the engine obtained either upon the activation of the controller or the start of the engine.

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.

A marine outboard motor for a marine vessel is provided. The marine outboard motor includes an internal combustion engine, a drive shaft configured to transmit a drive force from the internal combustion engine, a propeller shaft, and a drive transmission configured to transmit the drive force from the drive shaft to the propeller shaft. The motor also includes a lubrication system configured to convey lubricant along a lubricant flow path to lubricate one or both of the drive transmission and the drive shaft, and a lubricant filter provided along the lubricant flow path and configured to remove solid contaminants from the lubricant as it flows along the lubricant flow path. The lubricant filter is configured to be driven by the drive shaft.

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.

An outboard motor includes a bracket, an engine, an upper case, a lower case, a cavitation plate, a transmission, a cooling water passage, a first pump, and a second pump. The transmission includes a drive shaft and a propeller shaft. The cooling water passage is connected to the engine and located in the upper case and the lower case. The first pump is below a lower end of the bracket. The first pump is connected to the transmission and operable to send cooling water to the engine through the cooling water passage. The first pump is a non-positive displacement pump. The second pump is driven by a driving force from the transmission and operable to send the cooling water to the engine through the cooling water passage.