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.

A marine propulsion device includes a first gear, a second gear, a third gear, a case, a partition wall, and a first flow path. The case includes an internal space in which the first gear, the second gear, and the third gear are located. The partition wall is located between the second gear and the third gear in the internal space. The partition wall partitions the internal space into a first space and a second space. The second gear is located in the first space. The third gear is located in the second space. The first flow path communicates the first space with the second space. The first flow path is located on a same side as the first gear with respect to a center line of the second gear and the third gear.

A marine vessel propulsion machine ventilation apparatus includes a first ventilation film (31), a second ventilation film (35), and an air chamber (27). The first ventilation film (31) permits passing of a gas, prevents passing of a liquid, and has one film surface facing the outside. The second ventilation film (35) permits passing of a gas, prevents passing of a liquid, and has one film surface facing the inside of a device accommodation case (19). Another film surface of each of the first ventilation film (31) and the second ventilation film (35) faces the air chamber (27).

An outboard marine engine comprises an internal combustion engine; a lower gearcase, a set of gears disposed in the lower gearcase, the set of gears being configured to transfer power from the internal combustion engine to drive a propulsor to generate a thrust on the outboard marine engine, and a dipstick that extends into the lower gearcase. The dipstick is removable from the lower gearcase and configured to indicate a level of lubrication in the lower gearcase.

An outboard propulsion system comprising: a first portion for attachment to a boat comprising a stern, the first portion comprising an engine including a crankshaft; and a second portion comprising at least one propeller shaft having a longitudinal axis along the elongate length of the at least one propeller shaft, wherein the at least one propeller shaft is operably connected to the crankshaft via at least one drive shaft configured to transmit motive power therebetween, wherein the at least one drive shaft comprises a drop shaft and wherein the drop shaft is substantially perpendicular to the at least one propeller shaft, wherein the second portion is configured to pivot relative to the first portion about a steering axis, wherein the steering axis intersects the longitudinal axis of the at least one propeller shaft at an obtuse angle, wherein the first portion and second portion are configured to tilt together about a single axis of rotation substantially parallel to the stern of the boat, and wherein the first portion is fixed about a substantially vertical axis.

An outboard motor for a marine vessel application, transmission devices for such an outboard motor, and related methods of making, operating, and modifying attributes of same, are disclosed herein. In at least one embodiment, the motor includes a horizontal-crankshaft engine in an upper portion of the motor, positioned substantially above a trimming axis of the motor. In at least another embodiment, first, second and third transmission devices are employed to transmit rotational power from the engine to propeller(s). In at least a further embodiment, the 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 motor includes numerous cooling, exhaust, and/or oil system components, and/or other transmission features. In at least some additional embodiments, a transmission device of the motor is configured to facilitate gear ratio variation and/or includes an integrated oil pump.

An outboard marine engine comprises a vertically-aligned bank of piston-cylinders. An axially elongated camshaft operates a plurality of valves for controlling flow of air with respect to the vertically-aligned bank of piston-cylinders. The camshaft vertically extends between a lower camshaft end and an upper camshaft end. A lubricant passage axially conveys lubricant through the camshaft. An air outlet is located at the upper camshaft end. A valve is configured to open and close the air outlet to thereby facilitate lubrication of the plurality of valves at startup of the outboard marine engine.

An electric shift actuator is provided in an engine cover in which an engine of an upper unit is accommodated, a forward/reverse shift mechanism is provided in a lower unit, and a shift transmission mechanism including a clutch rod is provided to transmit driving force of the electric shift actuator to the forward/reverse shift mechanism by connecting the electric shift actuator with the forward/reverse shift mechanism, in which the clutch rod is disposed vertically in an intermediate unit on the rear side of a drive shaft that transmits driving force of the engine.

An outboard motor includes an electric motor including an output shaft extending in an upper-lower direction, a gearing connected to the output shaft of the electric motor and including gears to rotate around a rotation shafts extending in the upper-lower direction, and a housing chamber to accommodate the gearing and oil. The housing chamber includes a peripheral wall extending around one of the gears. The peripheral wall includes a sloped portion between the one gear and the peripheral wall that is inclined upward along a rotating direction of the gear.

An outboard motor having an internal combustion engine that causes rotation of a driveshaft, a planetary transmission that operatively connects the driveshaft to a transmission output shaft, a band brake configured to shift the planetary transmission amongst a forward gear, neutral gear and reverse gear, a hydraulic actuator is configured to actuate the band brake, and a cooling water circuit that extends adjacent to the hydraulic actuator so that the hydraulic actuator exchanges heat with cooling water in the cooling water circuit.