An outboard motor includes a first exhaust passage connected to an exhaust port and extending downward from the exhaust port through a support frame on a lateral side of a cylinder head. A first case accommodates an engine. A second case accommodates a propeller shaft. A third case is between the first case and the second case in a vertical direction. An exhaust pipe is between the first case and the second case in the vertical direction. The exhaust pipe is connected to the first exhaust passage. At least a portion of the exhaust pipe is outside the third case as seen in a side view of the outboard motor. An exterior cover is between the first case and the second case in the vertical direction. The exterior cover covers the exhaust pipe.

An outboard motor includes an engine, a pressure charger, an intercooler, a bypass air passage, and an air bypass valve to open and close the bypass air passage. The engine includes a cylinder block and an air intake passage and an exhaust passage both of which are connected to the cylinder block. The pressure charger is located in the air intake passage. The intercooler is located in the air intake passage between the cylinder block and the pressure charger. A first end of the bypass air passage is connected to a region of the air intake passage upstream of the pressure charger. A second end of the bypass air passage is connected to a region of the air intake passage downstream of the pressure charger. The air bypass valve is directly attached to the intercooler.

A marine propulsion unit is described. The marine propulsion unit allows for shallow, obstructed, or otherwise impeded operation of a vessel through a novel marine propulsion transfer unit that is, or can be, mechanically coupled to an outboard motor or other similar marine motor. A mount for raising and lowering the marine propulsion unit in a generally vertical direction allows for adjustment of operating depth of the marine propulsion unit to accommodate a wide range of operating conditions from shallow and obstructed water to traditional deep water operation.

An outboard motor includes a gear housing configured to rotatably house a propeller shaft that transmits a rotative power output from an engine to a propeller device. The gear housing includes a torpedo shape portion and a strut portion. The torpedo shape portion has a shape tapered toward a front side, and a shape biased upward toward the front side. The strut portion is disposed on an upper side of the torpedo shape portion. An outer peripheral surface of the torpedo shape portion is smoothly coupled to an outer peripheral surface of the strut portion via first to third curved surfaces. The first to third curved surfaces are each a curved surface inclined rearward and downward, a curved surface parallel to a front-rear direction, or a curved surface constituted of a part inclined rearward and downward and a part parallel to the front-rear direction.

An outboard motor includes a gear housing configured to rotatably house a propeller shaft that transmits a rotative power output from an engine to a propeller device. The gear housing includes a torpedo shape portion and a strut portion. The torpedo shape portion has a shape tapered toward a front side, and a shape biased upward toward the front side. The strut portion is disposed on an upper side of the torpedo shape portion. An outer peripheral surface of the torpedo shape portion is smoothly coupled to an outer peripheral surface of the strut portion via first to third curved surfaces. The first to third curved surfaces are each a curved surface inclined rearward and downward, a curved surface parallel to a front-rear direction, or a curved surface constituted of a part inclined rearward and downward and a part parallel to the front-rear direction.

An outboard motor for a marine vessel application, and related methods of making and operating same, are disclosed herein. In at least one embodiment, the outboard motor includes a horizontal-crankshaft engine in an upper portion of the outboard motor, positioned substantially positioned above a trimming axis of the outboard motor. In at least another embodiment, first, second and third transmission devices are employed to transmit rotational power from the engine to one or more propellers at a lower portion of the outboard motor. In at least a further embodiment, the outboard motor is made to include a rigid interior assembly formed by the engine, multiple transmission devices, and a further structural component. In further embodiments, the outboard motor includes numerous cooling, exhaust, and/or oil system components, as well as other transmission features.

An outboard motor for a marine vessel application, and related methods of making and operating same, are disclosed herein. In at least one embodiment, the outboard motor includes a horizontal-crankshaft engine in an upper portion of the outboard motor, positioned substantially positioned above a trimming axis of the outboard motor. In at least another embodiment, first, second and third transmission devices are employed to transmit rotational power from the engine to one or more propellers at a lower portion of the outboard motor. In at least a further embodiment, the outboard motor is made to include a rigid interior assembly formed by the engine, multiple transmission devices, and a further structural component. In further embodiments, the outboard motor includes numerous cooling, exhaust, and/or oil system components, as well as other transmission features.

A boat propulsion machine includes a power source, a drive shaft, a propeller, a gear mechanism, a gear case, a tank configured to store a cooling liquid for cooling the power source, a heat sink configured to cool the cooling liquid, a cooling liquid passage connecting the power source and the heat sink, and a pump a pump configured to pump the cooling liquid to circulate through the cooling liquid passage. The power source, the tank, and the pump are provided at an upper portion of the boat propulsion machine. The gear case is provided at a lower portion of the boat propulsion machine. The drive shaft extends in an upper-lower direction between the power source and the gear mechanism. The heat sink is provided at a position lower than the power source and higher than the gear case in the boat propulsion machine.

A boat propulsion machine includes a power source, a drive shaft, a propeller, a gear mechanism, a gear case, a tank configured to store a cooling liquid for cooling the power source, a heat sink configured to cool the cooling liquid, a cooling liquid passage connecting the power source and the heat sink, and a pump a pump configured to pump the cooling liquid to circulate through the cooling liquid passage. The power source, the tank, and the pump are provided at an upper portion of the boat propulsion machine. The gear case is provided at a lower portion of the boat propulsion machine. The drive shaft extends in an upper-lower direction between the power source and the gear mechanism. The heat sink is provided at a position lower than the power source and higher than the gear case in the boat propulsion machine.

An outboard motor includes a gear housing configured to rotatably house a propeller shaft that transmits a rotative power output from an engine to a propeller device. The gear housing includes a torpedo shape portion and a strut portion. The torpedo shape portion has a shape tapered toward a front side, and a shape biased upward toward the front side. The strut portion is disposed on an upper side of the torpedo shape portion. An outer peripheral surface of the torpedo shape portion is smoothly coupled to an outer peripheral surface of the strut portion via first to third curved surfaces. The first to third curved surfaces are each a curved surface inclined rearward and downward, a curved surface parallel to a front-rear direction, or a curved surface constituted of a part inclined rearward and downward and a part parallel to the front-rear direction.