A method for shifting a multi-speed transmission for transmitting rotation between an input shaft and an output shaft for a marine vessel. The method includes providing a multi-speed transmission having first and second gears engaged by actuating first and second clutches, and providing first and second pressure sensors that measure first and second pressures within the first and second clutches, respectively. The method further includes performing a first shift from the first gear to the second gear by de-actuating the first clutch a first delay after the second clutch is actuated, then measuring the first and second pressures and determining a first shift pressure at which the first and second pressures are substantially equal while performing the first shift. The method further includes comparing the first shift pressure to a first pressure threshold range and adjusting the first delay when the first shift pressure is outside the first pressure threshold range.

A method for shifting a marine propulsion device transmission between first and second gears transmitting torque from a powerhead with a redline RPM. The transmission has a transition time for completing a shift. The method includes measuring an RPM of the powerhead, comparing the RPM to a first threshold, and starting a timer when the RPM exceeds the first threshold. The method includes measuring the RPM of the powerhead after the first threshold is exceeded, comparing the RPM to a second threshold, stopping the timer when the RPM exceeds the second threshold, determining an elapsed time between starting and stopping the timer, and determining a shift RPM based on the determined elapsed time, the redline RPM, and the transition time of the transmission. The method includes controlling the transmission to shift when the RPM measured for the powerhead reaches the shift RPM such that shifting completes before the redline RPM.

A method for shifting a multi-speed transmission of a marine propulsion device between a first gear and a second gear each configured to transmit torque from a powerhead to a transmission output shaft. The method includes determining an actual power level requested for operating the marine propulsion device and measuring a transmission output shaft speed in which the transmission output shaft is rotating. The method further includes comparing the actual power level to a shift threshold, the shift threshold corresponding to expected power levels for operating the marine propulsion device as a function of the transmission output shaft speed of the transmission output shaft. The method further includes controlling the multi-speed transmission to shift when the actual power is outside the shift threshold.

A method for downshifting a multi-speed transmission of a marine propulsion device to a first gear from a second gear. The method includes providing a shift schedule that indicates a shift recommendation for when to downshift from the second gear to the first gear. The method further includes configuring the transmission to downshift when the shift schedule indicates the shift recommendation, determining a requested speed of the marine propulsion device, measuring an actual speed of the marine propulsion device, calculating an error between the requested speed and the actual speed, comparing the error to an error threshold, and determining when the error exceeds the error threshold longer than a duration threshold. The method further includes controlling the transmission to downshift, despite the shift schedule indicating a non-shift recommendation, when the duration threshold is exceeded so as to reduce the error between the requested speed and the actual speed.

A method is for making a marine drive for propelling a marine vessel in water. The method includes providing a gearcase; installing a propeller shaft assembly that extends forwardly from the gearcase; coupling front and rear propellers to the propeller shaft assembly, forwardly of the gearcase, such that rotation of the propeller shaft assembly causes rotation of the front and rear propellers, respectively, which thereby propels the marine vessel in the water; and reducing deleterious effects of cavitation on the gearcase by the combination of forming the gearcase with a wide trailing end portion, in particular to maintain pressure alongside the gearcase, and configuring the front and rear propellers so that the front propeller absorbs more torque/thrust load than the rear propeller during said rotation.

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.

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.

A power transmission device for an outboard motor, comprising a drive shaft, an endless loop flexible drive coupling and a propeller shaft, wherein the endless loop flexible drive coupling operatively connects said drive shaft to said propeller shaft for transferring output power from the drive shaft to the propeller shaft. The power transmission device comprises a first drive shaft, a second drive shaft, a first endless loop flexible drive coupling, a second endless loop flexible drive coupling, a first propeller shaft and a second propeller shaft, wherein the first propeller shaft is connected to the first drive shaft through the first endless loop flexible drive coupling to rotate the first propeller shaft in a first direction, and wherein the second propeller shaft is connected to the second drive shaft through the second endless loop flexible drive coupling to rotate the second propeller shaft in a second direction opposite to the first direction.

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.

The present invention concerns an outboard propulsion device for a navigational seacraft comprising a propulsion means (4), at least one engine (1) supplying torque to a drive shaft (20) extending out of the engine and driving a transmission shaft (3) intended to supply torque to the propulsion means, the drive shaft and the propulsion shaft being in a fixed relative orientation, and a transmission means (2) connected at the input to the drive shaft (20) in order to receive the engine torque and transmit it at least partially to the transmission shaft. The transmission means (2) modifies the orientation of the engine torque and transmits it, in the form of modified torque, to the transmission shaft (3) to which it is connected at the output, and the transmission shaft (3) is a double universal joint shaft (30, 31) that extends in an inclined manner between the transmission means (2) and the propulsion means (4), the transmission shaft at least partially transmitting the modified torque to the propulsion means.