A propulsion unit for a marine vessel is adapted to receive power from at least one power supply unit. The propulsion unit includes a stationary part adapted to be mounted to a hull of the marine vessel, and a movable part comprising one or more thrust generating devices adapted to transform the received power into a thrust by acting on water carrying the marine vessel. The propulsion unit is adapted to receive exhaust gases from at least two internal combustion engines, wherein the movable part is adapted to release the exhaust gases into the water.

A propulsion unit for a marine vessel is adapted to receive power from at least one power supply unit. The propulsion unit includes a stationary part adapted to be mounted to a hull of the marine vessel, and a movable part comprising one or more thrust generating devices adapted to transform the received power into a thrust by acting on water carrying the marine vessel. The propulsion unit is adapted to receive exhaust gases from at least two internal combustion engines, wherein the movable part is adapted to release the exhaust gases into the water.

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 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 propeller device has a propeller hub which is elongated along the rotational axis and a propeller blade which radially extends from the propeller hub. The propeller hub and propeller blade are configured so that when the propeller device is forwardly rotated, a first portion of the propeller hub on a first side of the propeller blade encounters a positive pressure and a second portion of the propeller hub on an opposite, second side of the blade encounters a relatively lower pressure or suction, and further so that when the propeller device is reversely rotated, the second portion of the propeller hub encounters a positive pressure and the first portion of the propeller hub encounters a relatively lower pressure or suction. An exhaust vent hole is located in the first portion of the propeller hub and configured to vent exhaust gases from the marine drive via the propeller hub as the propeller device is reversely rotated, thereby enhancing reverse thrust performance of the propeller device.

An outboard motor that significantly reduces or prevents discoloration around an exhaust opening includes an engine, a drive shaft, a propeller shaft, a housing, an exhaust passage, a water intake passage, and a valve. The exhaust passage guides an exhaust gas from the engine toward the discharge chamber inside the housing. The water intake passage guides water, which enters an inside of the housing, to the discharge chamber when a forward propulsive force is generated. The valve regulates passage of the exhaust gas at the first opening due to water pressure when a forward propulsive force is generated. The valve permits the passage of exhaust gas at the first opening due to exhaust pressure when a backward propulsive force is generated.

A system for controlling exhaust flow from an internal combustion engine powering a marine propulsion device includes a primary exhaust conduit having an upstream end receiving exhaust gas from the internal combustion engine and a downstream end discharging exhaust gas to a body of water via a gearcase housing. A bypass exhaust conduit has an upstream end receiving exhaust gas from the primary exhaust conduit and a downstream end discharging exhaust gas from a bypass outlet of the marine propulsion device. A bypass valve is selectively openable to allow exhaust gas to flow through the bypass conduit. A control module is in signal communication with the bypass valve. The control module opens the bypass valve to divert the exhaust gas through the bypass conduit and out the bypass outlet in response to selection of a control mode of the marine propulsion device other than a default lever control mode.

A marine drive has a primary exhaust outlet on its lower gearcase that discharges a primary flow of exhaust gas from the engine to seawater in which the marine drive is situated. A secondary exhaust outlet is located on the marine drive above the primary exhaust outlet and discharges a secondary flow of exhaust gas from the engine to atmosphere around the marine drive at least when the engine is operated at an idle speed. A tertiary exhaust outlet is located on the marine drive between the primary and secondary exhaust outlets, and discharges a tertiary flow of exhaust gas from the engine to the seawater or to the atmosphere depending upon a current location of the tertiary exhaust outlet with respect to the seawater. A muffler is configured to reduce noise emanating from the tertiary exhaust outlet.

A marine drive has a primary exhaust outlet on its lower gearcase that discharges a primary flow of exhaust gas from the engine to seawater in which the marine drive is situated. A secondary exhaust outlet is located on the marine drive above the primary exhaust outlet and discharges a secondary flow of exhaust gas from the engine to atmosphere around the marine drive at least when the engine is operated at an idle speed. A tertiary exhaust outlet is located on the marine drive between the primary and secondary exhaust outlets, and discharges a tertiary flow of exhaust gas from the engine to the seawater or to the atmosphere depending upon a current location of the tertiary exhaust outlet with respect to the seawater. A muffler is configured to reduce noise emanating from the tertiary exhaust outlet.

An outboard motor includes an engine, a propeller shaft, a propeller attached to the propeller shaft, a transmission to transmit rotation of the engine to the propeller shaft, an upper accommodation body accommodating a portion of the engine, a lower accommodation body accommodating a portion of the propeller shaft, and a steering to cause the lower accommodation body to rotate about a steering axis with respect to the upper accommodation body. The upper accommodation body includes an upper exhaust channel including an upper exhaust port that communicates with the engine. The lower accommodation body includes a lower exhaust channel including a lower exhaust port. The upper exhaust channel and the lower exhaust channel are switchable between a communication state of communicating with each other and a non-communication state of not communicating with each other based on a rudder angle of the steering.