There is provided a ship propulsion machine including: a drive shaft; a drive gear fixed to the drive shaft; a front gear meshed with the drive gear; a rear gear meshed with the drive gear; a rear propeller provided on an inner propeller shaft; a front propeller provided on an outer propeller shaft; a casing having a gear chamber; a second bearing that supports a front end side of the outer propeller shaft at a rear portion of the casing; a third bearing that supports the inner propeller shaft and the outer propeller shaft in a manner rotatable with respect to each other. The third bearing is disposed on an inner peripheral side of a shaft portion of the rear gear, and the second bearing is disposed on an outer peripheral side of the shaft portion of the rear gear.

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 drive system is provided for propelling a ship through water. The drive system has two propellers. The propellers are coaxial so that one propeller engages the incoming water first, and the other propeller engages the water after it passes through the first propeller. The drive system has a stator that causes a first rotor to rotate. The first rotor is connected to, the first propeller to cause the first propeller to rotate. The first rotor also causes a second rotor to rotate. The second rotor is connected to the second propeller to cause the second propeller to rotate.

A drive system is provided for propelling a ship through water. The drive system has two propellers. The propellers are coaxial so that one propeller engages the incoming water first, and the other propeller engages the water after it passes through the first propeller. The drive system has a stator that causes a first rotor to rotate. The first rotor is connected to, the first propeller to cause the first propeller to rotate. The first rotor also causes a second rotor to rotate. The second rotor is connected to the second propeller to cause the second propeller to rotate.

A lower unit for a marine propulsion device includes a gearcase housing defined along a longitudinal center axis between a fore end and an aft end. A propulsor shaft extends through the gearcase housing along the longitudinal axis. A driveshaft extends non-parallel to the propulsor shaft and rotates in a direction of rotation when powered by an engine. The driveshaft is coupled in torque-transmitting relationship with the propulsor shaft. A skeg projects from a bottom surface of the gearcase housing proximate at least the aft end thereof. The skeg or the gearcase housing is cambered such that a moment acting in a direction opposite the driveshaft's direction of rotation is induced on the skeg or the gearcase housing as the lower unit moves through water. A marine propulsion device is also disclosed.

A lower unit for a marine propulsion device includes a gearcase housing defined along a longitudinal center axis between a fore end and an aft end. A propulsor shaft extends through the gearcase housing along the longitudinal axis. A driveshaft extends non-parallel to the propulsor shaft and rotates in a direction of rotation when powered by an engine. The driveshaft is coupled in torque-transmitting relationship with the propulsor shaft. A skeg projects from a bottom surface of the gearcase housing proximate at least the aft end thereof. The skeg or the gearcase housing is cambered such that a moment acting in a direction opposite the driveshaft's direction of rotation is induced on the skeg or the gearcase housing as the lower unit moves through water. A marine propulsion device is also disclosed.

A drive system is provided for propelling a ship through water. The drive system has two propellers. The propellers are coaxial so that one propeller engages the incoming water first, and the other propeller engages the water after it passes through the first propeller. The drive system has a stator that causes a first rotor to rotate. The first rotor is connected to, the first propeller to cause the first propeller to rotate. The first rotor also causes a second rotor to rotate. The second rotor is connected to the second propeller to cause the second propeller to rotate.

A drive system is provided for propelling a ship through water. The drive system has two propellers. The propellers are coaxial so that one propeller engages the incoming water first, and the other propeller engages the water after it passes through the first propeller. The drive system has a stator that causes a first rotor to rotate. The first rotor is connected to, the first propeller to cause the first propeller to rotate. The first rotor also causes a second rotor to rotate. The second rotor is connected to the second propeller to cause the second propeller to rotate.

A marine propulsion system, supported by a strut, comprising an inner propeller shaft supporting a first propeller adjacent a trailing end thereof, and the inner propeller shaft is connected to the drive shaft for receiving and supplying a first portion of torque to the first propeller as well as transfer thrust, generated by the first propeller, along the inner propeller shaft back to the drive shaft. An outer propeller shaft supports a second propeller adjacent a trailing and thereof, and the outer propeller shaft surrounds the inner propeller shaft. A differential gear set receives a second portion of the torque and supplies the second portion to the outer propeller shaft so that the second propeller rotates in an opposite rotational direction to the first propeller. The thrust, generated by the first and the second propellers, is conveyed along either the inner or the outer propeller shafts, to the drive shaft.