Abstract: An internal combustion engine is provided with: two intake pipe portions for guiding intake air to two banks; and a blow-by gas recirculation pathway for leading blow-by gas to the two intake pipe portions from a cylinder head or a crank case that includes the two banks. The blow-by gas recirculation pathway includes a distribution passage which is provided between the two intake pipe portions, and which distributes the blow-by gas and allows the same to flow to the two intake pipe portions.

Abstract: An internal combustion engine is provided with: two intake pipe portions for guiding intake air to two banks; and a blow-by gas recirculation pathway for leading blow-by gas to the two intake pipe portions from a cylinder head or a crank case that includes the two banks. The blow-by gas recirculation pathway includes a distribution passage which is provided between the two intake pipe portions, and which distributes the blow-by gas and allows the same to flow to the two intake pipe portions.

Abstract: An internal oil strainer housed in an outboard motor unit. A lower end of an oil tube is supported by a first seal member constructed of an O-ring fitted into an oil outlet of a strainer case. An upper end of the oil tube is supported by a second seal member constructed of an O-ring fitted into an inlet of an oil channel.

Abstract: An engine for an outboard motor includes an oil filter. A first oil passage has a communication duct disposed at a position lower than that of the oil filter and communicating with a crank chamber. The communication duct is closed by a drain valve that can be opened and closed manually. Opening the drain valve allows the oil accumulated in the first oil passage to flow down into the crank chamber through the communication duct.

Abstract: Exhaust passage system in an outboard engine unit includes: an engine-side exhaust pipe; a downstream exhaust pipe for directing exhaust gas downstream from the engine-side exhaust pipe, a lower end portion of the engine-side exhaust pipe and an upper end portion of the downstream exhaust pipe being positioned in horizontally parallel to each other and horizontally overlap each other so as to provide fluid communication therebetween via a through-hole formed in the overlapping portions of the end portions; and a vertical partition wall provided, in an upper end region of the overlapping portions for hampering back-flows of fluid.

Abstract: An internal oil strainer housed in an outboard motor unit. A lower end of an oil tube is supported by a first seal member constructed of an O-ring fitted into an oil outlet of a strainer case. An upper end of the oil tube is supported by a second seal member constructed of an O-ring fitted into an inlet of an oil channel.

Abstract: Exhaust passage system in an outboard engine unit includes: an engine-side exhaust pipe; a downstream exhaust pipe for directing exhaust gas downstream from the engine-side exhaust pipe, a lower end portion of the engine-side exhaust pipe and an upper end portion of the downstream exhaust pipe being positioned in horizontally parallel to each other and horizontally overlap each other so as to provide fluid communication therebetween via a through-hole formed in the overlapping portions of the end portions; and a vertical partition wall provided, in an upper end region of the overlapping portions for hampering back-flows of fluid.

Abstract: An engine for an outboard motor includes an oil filter. A first oil passage has a communication duct disposed at a position lower than that of the oil filter and communicating with a crank chamber. The communication duct is closed by a drain valve that can be opened and closed manually. Opening the drain valve allows the oil accumulated in the first oil passage to flow down into the crank chamber through the communication duct.

Abstract: An outboard motor steering system includes a hydraulic fluid supply mechanism connected to the steering hydraulic cylinder to supply hydraulic fluid thereto disposed in a space formed between the stern brackets and the swivel case. In other words, since the hydraulic fluid supply mechanism is incorporated into the outboard motor as a unit, the structure can be made simpler than that of the related art and the number of parts in the entire system can be reduced and moreover the work of installation into the boat's hull can be simplified. Also, operating efficiency is improved for an electric motor serving as the source of driving force for a hydraulic pump that supplies hydraulic fluid to the hydraulic cylinder used for steering, and power consumption is reduced.

Abstract: An outboard motor hydraulic mechanism having a hydraulic actuator moving the outboard motor about a rotary shaft relative to a boat the motor is mounted on and a hydraulic pump and a plurality of electric motors connected to the pump. A number of the motors to be operated is determined based on an estimated load acting on the actuator, output shafts of the motors are aligned coaxially with a drive shaft of the pump, and they are directly connected with each other. This ensures that the operator is prevented from having an unpleasant feeling, lowers electric power consumption by the motors, and reduces the number of components and simplifies the structure of the mechanism.

Abstract: An outboard motor hydraulic mechanism having a hydraulic actuator moving the outboard motor about a rotary shaft relative to a boat the motor is mounted on and a hydraulic pump and a plurality of electric motors connected to the pump. A number of the motors to be operated is determined based on an estimated load acting on the actuator, output shafts of the motors are aligned coaxially with a drive shaft of the pump, and they are directly connected with each other. This ensures that the operator is prevented from having an unpleasant feeling, lowers electric power consumption by the motors, and reduces the number of components and simplifies the structure of the mechanism.

Abstract: Recesses are provided in portions of a head cover and a crankcase which are opposed to outer peripheries of a timing chain and a balancer-driving chain driven by a crankshaft of a vertical engine, whereby vertical walls and horizontal walls are formed to oppose to outer peripheral surfaces and lower surfaces of the timing chain and the balancer-driving chain. An oil scattered from the timing chain and the balancer-driving chain by a centrifugal force is caught on the vertical walls, and the oil flowing down along the vertical walls by gravitation is retained on the underlying horizontal walls, whereby the oil can be brought into contact with the chains without waste to effectively lubricate the chains.

Abstract: In an outboard motor air intake system, there are equipped with a secondary air passage connected to an air intake pipe at a location downstream of the throttle valve in terms of intake air flow; a manual valve installed in the secondary air passage to be operable by the operator to regulate a sectional area of the secondary air passage, a knob positioned at a location remote from the outboard motor to be operable by the operator, and a wire connecting the knob to the manual valve, such that the sectional area of the secondary air passage can be regulated through the knob and the manual valve at the location remote from the outboard motor, thereby making it easy to realize fine regulation when the engine operates in a low-speed such as idling.

Abstract: In an outboard engine system, an exhaust manifold fixed to a cylinder head of a vertical engine by a bolt includes single pipe portions and a collecting portion through which an exhaust gas flow. A water jacket, through which cooling water flows, is formed to surround a periphery of the collecting portion. An exhaust characteristics sensor for detecting an oxygen content of exhaust gas is mounted to an upper surface of the exhaust manifold. A water temperature sensor for detecting temperature of the cooling water is mounted to a side surface of the exhaust manifold.

Abstract: Oil jets are mounted in upper two cylinders in a cylinder block of a 4-cylinder vertical engine to inject an oil to rear faces of pistons received in the two cylinders. Thus, although lower pistons are cooled more effectively by the oil dropped by gravitation through oil return bores provided in journal support walls, the upper pistons are forcibly cooled by the oil injected from the oil jets, so that the four pistons can be cooled equally to prevent insufficient cooling and excessive cooling, while minimizing the required amount of the oil.

Abstract: In an outboard engine system, a first opening communicating with a cooling water discharge passage and a second opening communicating with a cooling water supply passage are formed adjacent to each other in an upper wall of a cooling water passage forming member. A relief valve is provided in a first opening at a position remote from a tilt shaft. The relief valve includes a valve seat provided at the upper wall and facing downward. A valve body is seated on the valve seat from below. Accordingly, any cooling water staying in an upper portion of the relief valve leaks through gaps between the valve seat and the valve body to be discharged easily. When the outboard engine system is tilted upward about the tilt shaft, the opening provided with the relief valve is moved upward so that the cooling water is discharged smoothly through the other opening.

Abstract: In a water-cooled multi-cylinder vertical engine for an outboard engine system, cooling water having passed through an exhaust-manifold cooling water jacket for cooling an exhaust passage within an engine room is supplied to a cylinder-block cooling water jacket provided in a cylinder block through water supply pipes, a branching member and two upper and lower couplings. In this case, the lower coupling is locked below the center of a lowermost cylinder to minimize unevenness in flow rate of the cooling water flowing through a water jacket on opposite left and right sides of a cylinder toward a cooling water outlet provided at an upper portion thereof, thereby making uniform the distribution of the temperature around a combustion chamber, leading to an enhancement in cooling effect.

Abstract: In a vertical engine, a bulged portion protrudes upwards, in conformity to a partially cylindrical outer wall of uppermost one of cylinders, on an upper surface of a cylinder block forming a bottom wall of a chain chamber accommodating a chain for driving a camshaft and a balancer shaft through a crankshaft. A pair of oil return bores for returning an oil in the chain chamber to an oil pan are provided in lower portions of the bottom wall on opposite sides of an axis of the bulged portion. The oil which has lubricated the chain in the chain chamber flows so that it is distributed to the opposite sides of the axis, and the oil is returned smoothly from the oil return bores formed in the bottom wall to the oil pan.

Abstract: A water-cooled vertical engine includes a cylinder block cooling water jacket formed in a cylinder block and a cylinder head cooling water jacket formed in a cylinder head, the jackets being substantially independent. Cooling water from a cooling water pump is supplied to the cylinder block cooling water jacket via through holes, and cooling water branching just before the cylinder block cooling water jacket is supplied to the cylinder head cooling water jacket via a pair of cooling water passages through gasket faces of the cylinder block and the cylinder head.

Abstract: A first chain mechanism for transmitting the rotation of a crankshaft of an vertical engine to a camshaft and a second chain mechanism for transmitting the rotation of the crankshaft to a balancer shaft are forcibly lubricated by an oil injected by first, second and third oil jets mounted within a chain chamber. The first, second and third oil jets are disposed at locations closer to the crankshaft, the cam shaft and the balancer shaft, respectively, and the first and second oil jets are disposed inside a travel locus for a timing chain. Thus, the chain mechanisms disposed in a plane of the vertical engine can be lubricated effectively.