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.

An engine includes a crankshaft extending in a vertical direction. A drive shaft is connected to the crankshaft and coaxial with the crankshaft. A water intake passage is connected to the engine. A water pump is connected to the water intake passage. The water pump includes a pump shaft. The pump shaft is eccentrically mounted with respect to the drive shaft and parallel or substantially parallel to the drive shaft. The pump shaft rotates according to rotation of the drive shaft.

An engine includes a crankshaft extending in a vertical direction. A drive shaft is connected to the crankshaft and coaxial with the crankshaft. A water intake passage is connected to the engine. A water pump is connected to the water intake passage. The water pump includes a pump shaft. The pump shaft is eccentrically mounted with respect to the drive shaft and parallel or substantially parallel to the drive shaft. The pump shaft rotates according to rotation of 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.

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.

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. A heat exchanging member is provided that is positioned below an anticavitation plate and above a propeller shaft that rotationally drives the propeller, and inside the heat exchanging member, a cooling oil channel member is provided that cooling oil for cooling the motor flows through.

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. A heat exchanging member is provided that is positioned below an anticavitation plate and above a propeller shaft that rotationally drives the propeller, and inside the heat exchanging member, a cooling oil channel member is provided that cooling oil for cooling the motor flows through.

A closed loop heat exchanger system for use with an outboard motor, wherein the heat exchanger assembly is disposed in the housing portion of the lower drive unit of the outboard motor where the propulsion assembly resides. The heat exchanger assembly being in thermal communication with the external surface of the housing of the lower drive unit, thus eliminating the need for an external raw water intake on the lower housing portion and reducing or eliminating components associated with a raw water pump system.

A closed loop heat exchanger system for use with an outboard motor, wherein the heat exchanger assembly is disposed in the housing portion of the lower drive unit of the outboard motor where the propulsion assembly resides. The heat exchanger assembly being in thermal communication with the external surface of the housing of the lower drive unit, thus eliminating the need for an external raw water intake on the lower housing portion and reducing or eliminating components associated with a raw water pump system.