An outboard motor is provided with an upper separator disposed on the lower side of an oil case for storing a lubricating oil of an engine, and an extension case which is separably connected on the lower side of the upper separator. The upper separator has a central exhaust passage through which exhaust gas flows, and a cooling water flow part through which cooling water flows on the outside of the central exhaust passage, the central exhaust passage and the cooling water flow part forming an integrated structure. The exhaust gas and the cooling water are caused to mix in the extension case.

A forward/backward switching mechanism having an intermediate gear supported by an intermediate shaft perpendicular to a drive shaft is interposed between first and second input shafts. A clutch body is a dog clutch having upper and lower locking dogs. As the dog clutch moves along an axial direction of the second input shaft and is engaged with upper or lower gears, rotation of the first input shaft is forwardly or reversely transmitted to the second input shaft.

A forward/backward switching mechanism having an intermediate gear supported by an intermediate shaft perpendicular to a drive shaft is interposed between first and second input shafts. A clutch body is a dog clutch having upper and lower locking dogs. As the dog clutch moves along an axial direction of the second input shaft and is engaged with upper or lower gears, rotation of the first input shaft is forwardly or reversely transmitted to the second input shaft.

The invention provides an internal combustion engine comprising a piston mounted for reciprocating linear motion within a cylinder along a cylinder axis. The piston is coupled to an output shaft by a power transfer assembly arranged to convert linear motion of the piston to rotary motion of the output shaft. The piston has a first head moveable within a first chamber and a second head opposite the first head and moveable within a second chamber. The power transfer assembly has a lubrication system for lubricating moving components of the power transfer assembly. The lubrication system is sealed from the first chamber and the second chamber to prevent the passage of fluid from the lubrication system into the first chamber and the second chamber.

The invention provides an internal combustion engine comprising a piston mounted for reciprocating linear motion within a cylinder along a cylinder axis. The piston is coupled to an output shaft by a power transfer assembly arranged to convert linear motion of the piston to rotary motion of the output shaft. The piston has a first head moveable within a first chamber and a second head opposite the first head and moveable within a second chamber. The power transfer assembly has a lubrication system for lubricating moving components of the power transfer assembly. The lubrication system is sealed from the first chamber and the second chamber to prevent the passage of fluid from the lubrication system into the first chamber and the second chamber.

An outboard motor includes an engine, a first cooling water passage to cool a first cooling target including the engine and through which first cooling water including water from outside an outboard motor body passes, a first pump to pump the first cooling water from outside the outboard motor body to the first cooling water passage, a second cooling water passage to cool a second cooling target different from the first cooling target and through which second cooling water different from the first cooling water passes, and a second pump to pump the second cooling water to the second cooling water passage.

An outboard motor includes an engine, a first cooling water passage to cool a first cooling target including the engine and through which first cooling water including water from outside an outboard motor body passes, a first pump to pump the first cooling water from outside the outboard motor body to the first cooling water passage, a second cooling water passage to cool a second cooling target different from the first cooling target and through which second cooling water different from the first cooling water passes, and a second pump to pump the second cooling water to the second cooling water passage.

An outboard-motor vibration-isolating cooler system method providing a retrofit substitute for the midsection and the lower unit of a standard outboard motor, having a substitute closed-loop cooling system with an exterior heat exchanger, a substitute oil reservoir, a substitute exhaust system, and a substitute propulsion system with an isolating power-take-off shaft, allowing an existing standard outboard-motor powerhead to be used in conditions not conducive to standard open-loop water cooling, such as shallow-water, muddy-water, obstructed-water, seawater, or corrosive-water conditions.

An outboard-motor vibration-isolating cooler system method providing a retrofit substitute for the midsection and the lower unit of a standard outboard motor, having a substitute closed-loop cooling system with an exterior heat exchanger, a substitute oil reservoir, a substitute exhaust system, and a substitute propulsion system with an isolating power-take-off shaft, allowing an existing standard outboard-motor powerhead to be used in conditions not conducive to standard open-loop water cooling, such as shallow-water, muddy-water, obstructed-water, seawater, or corrosive-water conditions.

Embodiments of outboard motors and related systems and components thereof, as well as arrangements of marine vessels implementing same, as well as related methods of operation, use, assembly, and manufacture, and related improvements, are disclosed herein. In at least some embodiments, the outboard motor includes a cowling system in which at least one divider portion separates an interior region into first and second portion, with the transmission and engine respectively being situated in the first and second portions, respectively. Additionally, in at least some embodiments, the outboard motor includes a water pump system in which a water pump is integrated with the transmission. Further, in at least some embodiments, the outboard motor includes a fuel vaporization suppression feature, or an oil tank feature that allows for desirable oil drainage from the engine of the outboard motor particularly when the outboard motor is in particular (e.g., storage) positions.