An internal combustion engine includes a first blow-by gas passage defined in a second wall. The internal combustion engine includes a second blow-by gas passage defined in a third wall. The internal combustion engine includes a third blow-by gas passage defined in a fourth wall. The first blow-by gas passage to the third blow-by gas passage connect an oil chamber and an oil separator to each other. The second wall includes a first connecting path. The fourth wall includes a second connecting path. The first connecting path connects the first crank chamber and the second crank chamber. The second connecting path connects the third crank chamber and the fourth crank chamber to each other. The third wall does not have a passage connecting the second crank chamber and the third crank chamber to each other.

A marine propulsion device includes a controller configured or programmed to perform a control to suppress an engine rotation speed. The controller is configured or programmed to perform an initial misfire control to determine whether or not a cylinder of the engine is caused to misfire in order to suppress the engine rotation speed when it is determined that an initial sudden increase in the engine rotation speed that causes over-revving has occurred based on a detection result from a rev-up detector, and perform a subsequent misfire control to determine whether or not the cylinder is caused to misfire in order to suppress the engine rotation speed when it is determined that a subsequent sudden increase in the engine rotation speed that causes the over-revving has occurred following the initial sudden increase in the engine rotation speed based on the detection result from the rev-up detector.

A forced-induction device includes a turbine wheel and a partition wall that partitions the interior of a connection pipe into a first passage and a second passage. When viewed in a cross section orthogonal to a rotation axis of the turbine wheel, a line segment connecting the rotation center of the turbine wheel and a downstream end of an inner wall in a flow direction of exhaust gas is a first line segment. A straight line orthogonal to the first line segment and extending from the downstream end in the flow direction of the exhaust gas is a first imaginary line. A straight line passing through a proximal end of the partition wall and orthogonal to an inflow direction of the exhaust gas is a second imaginary line. The distal end of the partition wall is located between the first imaginary line and the second imaginary line.

A forced-induction device includes a turbine wheel and a partition wall that partitions the interior of a connection pipe into a first passage and a second passage. When viewed in a cross section orthogonal to a rotation axis of the turbine wheel, a line segment connecting the rotation center of the turbine wheel and a downstream end of an inner wall in a flow direction of exhaust gas is a first line segment. A straight line orthogonal to the first line segment and extending from the downstream end in the flow direction of the exhaust gas is a first imaginary line. A straight line passing through a proximal end of the partition wall and orthogonal to an inflow direction of the exhaust gas is a second imaginary line. The distal end of the partition wall is located between the first imaginary line and the second imaginary line.

A forced-induction device includes a turbine wheel, a turbine housing, and a connection pipe. The connection pipe includes a partition wall that partitions the inside of the connection pipe into a first passage and a second passage. When a cross section orthogonal to a rotation axis of the turbine wheel is viewed, a line segment extending from the distal end of the partition wall toward the upstream side in the flow direction of exhaust gas and defining a boundary between the first passage and the partition wall is a first downstream line segment. A line segment extending from the distal end of the partition wall toward the upstream side in the flow direction of exhaust gas and defining a boundary between the second passage and the partition wall is a second downstream line segment. The first downstream line segment and the second downstream line segment are parallel to each other.

An internal combustion engine includes a first blow-by gas passage defined in a second wall. The internal combustion engine includes a second blow-by gas passage defined in a third wall. The internal combustion engine includes a third blow-by gas passage defined in a fourth wall. The first blow-by gas passage to the third blow-by gas passage connect an oil chamber and an oil separator to each other. The second wall includes a first connecting path. The fourth wall includes a second connecting path. The first connecting path connects the first crank chamber and the second crank chamber. The second connecting path connects the third crank chamber and the fourth crank chamber to each other. The third wall does not have a passage connecting the second crank chamber and the third crank chamber to each other.

A forced-induction device includes a turbine wheel, a turbine housing, and a connection pipe. The connection pipe includes a partition wall that partitions the inside of the connection pipe into a first passage and a second passage. When a cross section orthogonal to a rotation axis of the turbine wheel is viewed, a line segment extending from the distal end of the partition wall toward the upstream side in the flow direction of exhaust gas and defining a boundary between the first passage and the partition wall is a first downstream line segment. A line segment extending from the distal end of the partition wall toward the upstream side in the flow direction of exhaust gas and defining a boundary between the second passage and the partition wall is a second downstream line segment. The first downstream line segment and the second downstream line segment are parallel to each other.

A power device includes: a plurality of shafts; and a case that rotatably supports the plurality of shafts. Each of the plurality of shafts has a protruding end portion protruding outward from the case at least at one end portion in an axial direction. An output unit capable of rotationally driving a driven device is configured at the protruding end portion.

An internal combustion engine includes one or more unopposed cylinder units where each cylinder unit drives the crankshaft via a yoke assembly rather than a conventional connecting rod. The yoke assembly is formed by a connecting rod assembly that can have an upper portion having a connecting member connected to the piston, and a lower portion. The connecting rod assembly moves exclusively along the bore axis of the cylinder, with no side to side motion. The connecting rod assembly also defines a transverse slot in the yoke portion in which a connecting rod bearing housing reciprocates with motion of a connecting rod journal on the crankshaft within the transverse slot. Since the motion of the connecting rod is linear, and the connecting rod bearing housing moves circularly, there are no secondary forces resulting in an inline engine using the unopposed cylinder unit configuration.

An exhaust manifold may include first to fourth exhaust pipes respectively connected to first to fourth cylinders which is sequentially disposed in an engine, the exhaust manifold may include a first exhaust manifold including the second exhaust pipe connected to the second cylinder and the third exhaust pipe connected to the third cylinder; a second exhaust manifold including the first exhaust pipe connected to the first cylinder, the fourth exhaust pipe connected to the fourth cylinder and the first exhaust pipe, and a recirculation valve apparatus mounted in the first exhaust pipe; wherein the second exhaust pipe and the third exhaust pipe are directly connected to a converter housing for mounting a catalytic converter in which purifies exhaust gas, and wherein the fourth exhaust pipe is connected to the first exhaust pipe at upstream of the recirculation valve, and the first exhaust pipe is directly connected to the converter housing.