A method of automatically controlling trim position of a marine drive with a control system on a marine vessel includes receiving a user-selected command associated with wake surfing and then controlling a trim actuator to automatically position the marine drive in a tucked position, tucked position is between a vertical trim position and a minimum running trim position. Once a vessel condition of the marine vessel reaches a first threshold vessel condition the trim actuator is controlled to trim up the marine drive to a predetermined target trim position to generate wave behind the marine vessel. The first threshold vessel condition is at least one of a threshold vessel speed, a threshold engine speed, a threshold engine load, and a threshold vessel pitch.

A cowling has first and second cowl portions that enclose a powerhead on a marine drive. A latching assembly is for latching the first and second cowl portions together. The latching assembly has a retainer portion fixed to the first cowl portion and a latching portion fixed to the second cowl portion. The latching portion comprises a latch arm and a bell crank, the latch arm and bell crank being rotatable into and between a latched position in which the latch arm is latched to the retainer portion and an unlatched position in which the latch arm is unlatched from the retainer portion. A novel detent mechanism mechanically retains the latch arm and bell crank in the latched position and alternately in the unlatched position. A pair of bolted connections that fix the first and second cowling portions together and are located on opposite sides of the cowling.

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 marine engine assembly is provided for propelling a marine vessel. The marine engine assembly includes an internal combustion engine configured to drive a propulsion arrangement, a turbocharger comprising a turbine portion having a turbine outlet, and a turbocharger exhaust conduit coupled to the turbine outlet. The turbocharger exhaust conduit acts as a primary support to the turbocharger within the marine engine assembly.

An objective of the disclosure is to provide a simulation method for a two-stage plunger pressurized common rail fuel system of a marine low-speed engine. The method includes: first setting initial status parameters, such as a control step of a system model, a total time of a calculation process, and structure parameters and pressures of components; and then establishing a mathematical model of a fuel booster unit, a mathematical model of a high-pressure fuel pipe and a mathematical model of a fuel injector based on a MATLAB simulation platform, and connecting input and output parameters of the models to realize data transfer between the models. By considering one-dimensional (1D) spatial fluctuations in the high-pressure fuel pipe, the disclosure establishes a high-precision model of the fuel system, which provides an effective method for designing and calculating detailed pressures in the common rail fuel system.

A noise reduction system for a marine vessel having a plurality of marine propulsion devices including a first marine propulsion device and a second marine propulsion device, each of the plurality of marine propulsion devices including a drive source, each of the drive sources operating on a same principle as that of the other drive sources, and including a rotary member. The noise reduction system includes a controller configured to control rotation of the rotary member of the drive source in the second marine propulsion device, to thereby control a phase of a second noise caused thereby, such that a first noise caused by rotation of the rotary member of the drive source in the first marine propulsion device is canceled by the second noise.

A valve device includes: a flow path forming member having a first flow path through which a fluid is to flow, and a conical second flow path formed on a downstream side of the first flow path and having an outer diameter increasing in a flow direction of the first flow path; a spherical valve body capable of blocking a flow of the fluid in the first flow path by contacting an inner surface of the flow path forming member, which forms the second flow path; a holding member configured to hold the valve body in a conical concave part; and a coil-shaped spring configured to apply a force in a direction of causing the valve body to contact the inner surface via the holding member and arranged so that a direction of a center line of the coil is tilted with respect to the flow direction.

Engine includes: crankcase housing crankshaft extending in vertical direction; cylinder block mounted on side of crankcase and formed with cylinder; cylinder head mounted on side of cylinder block and provided with air inlet port and air outlet port communicating with cylinder; cylinder head cover mounted on side of cylinder head and covering air inlet port and air outlet port; mount case including: supporting portion provided below crankcase and cylinder block and supporting crankcase and cylinder block; and extending portion extending from supporting portion below cylinder head and cylinder head cover; oil pan provided below mount case and storing lubricating oil; and communication tube communicating first space formed between cylinder head and cylinder head cover and second space formed between mount case and oil pan. Communication tube is provided between cylinder head cover and extending portion.

An engine includes: a crankshaft disposed vertically; a piston that is connected to the crankshaft via a connecting rod and reciprocates in a cylinder; a cylinder head forming a combustion chamber of the cylinder at an end face of a movable portion of the piston; an intake valve and an exhaust valve disposed at the cylinder head, the intake valve being configured to take in fuel-air mixture, which is a mixture of fuel and air, the exhaust valve being configured to exhaust the fuel-air mixture; a low-rotation rocker arm (rocker arm) that drives the intake valve and the exhaust valve by rotation of a cam shaft; and a rocker shaft that supports the low-rotation rocker arm such that the low-rotation rocker arm is swingable, and an oil holding portion extending in an axial direction of the rocker shaft is provided between the rocker shaft and the low-rotation rocker arm.

A cover structure of an upper unit in which a power source of an outboard motor is provided, the cover structure includes a main body cover including a pair of divided covers connected to each other, the pair of the divided covers being configured to be divided into each other in a left-right direction with respect to a traveling direction of a boat, and an attachable and detachable cover that is attachable to and detachable from a part of an outer surface of at least one of the pair of the divided covers.