Abstract: Constraints on arrangement of catalysts are reduced, and early activation and long-term performance maintenance of the catalysts are both achieved. An exhaust pipe includes a first catalyst provided in a first exhaust pipe extending upward on the side of an exhaust manifold, and a second catalyst provided in a second exhaust pipe that extends downward from a bent pipe extending from the first exhaust pipe and that is adjacent to the first exhaust pipe. The second catalyst is disposed at a position offset to a higher location from an up-down middle position of the first exhaust pipe.

Abstract: An exhaust gas purification structure of an outboard motor includes an exhaust gas pipe that has an exhaust gas passage through which exhaust gas of an engine can flow; and a catalyst that is provided in the exhaust gas passage and purifies the exhaust gas by allowing the exhaust gas to pass through the inside thereof. The exhaust gas pipe includes a coolant flow passage allowing a coolant that cools the exhaust gas to flow therethrough. An exhaust gas bypass passage allowing the exhaust gas to flow without passing through the catalyst is formed between the catalyst and an inner surface of the exhaust gas pipe forming the exhaust gas passage.

Abstract: Constraints on arrangement of catalysts are reduced, and early activation and long-term performance maintenance of the catalysts are both achieved. An exhaust pipe includes a first catalyst provided in a first exhaust pipe extending upward on the side of an exhaust manifold, and a second catalyst provided in a second exhaust pipe that extends downward from a bent pipe extending from the first exhaust pipe and that is adjacent to the first exhaust pipe. The second catalyst is disposed at a position offset to a higher location from an up-down middle position of the first exhaust pipe.

Abstract: An exhaust gas purification structure of an outboard motor includes an exhaust gas pipe that has an exhaust gas passage through which exhaust gas of an engine can flow; and a catalyst that is provided in the exhaust gas passage and purifies the exhaust gas by allowing the exhaust gas to pass through the inside thereof. The exhaust gas pipe includes a coolant flow passage allowing a coolant that cools the exhaust gas to flow therethrough. An exhaust gas bypass passage allowing the exhaust gas to flow without passing through the catalyst is formed between the catalyst and an inner surface of the exhaust gas pipe forming the exhaust gas passage.

Abstract: In an outboard motor adapted to be mounted on a hull and equipped with an engine having a crankshaft located parallel with a gravity axis and a vertical shaft connected to the crankshaft to be rotated around the gravity axis, an urger is disposed at a position between the crankshaft and the vertical shaft to urge the crankshaft upward in a direction parallel with the gravity axis.

Abstract: In an outboard motor adapted to be mounted on a hull and equipped with an engine having a crankshaft located parallel with a gravity axis and a vertical shaft connected to the crankshaft to be rotated around the gravity axis, an urger is disposed at a position between the crankshaft and the vertical shaft to urge the crankshaft upward in a direction parallel with the gravity axis.

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: 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 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.

Abstract: A base member mounted to a side of a cylinder block is formed with an inlet-side oil supply passage for supplying an oil to an oil filter, and an outlet-side oil supply passage for discharging the oil from the oil filter. As a result, it is unnecessary to increase the thickness of a wall of the cylinder block or to form a bulged portion in order to form the oil supply passages, thereby contributing to a decrease in weight of the cylinder block. Moreover, because the oil supply passages are formed in the base member, the layouts thereof can be determined freely without restrained by the shape of the cylinder block, thereby contributing an increase in degree of freedom for the design.

Abstract: In an engine intake A/F ratio control system in an outboard engine system, a secondary air passage (P) for supplying secondary air for regulating the A/F ratio of an air-fuel mixture is connected to a carburetor (33) in an intake system of an engine (E), and a duty control valve (68) is connected to the secondary air passage (P). A duty control unit (92) is connected to the duty control valve (68) for controlling the duty ratio of a pulse applied to a coil (76) of the duty control valve (68), and an LAF sensor (94) is mounted to an exhaust system for detecting an A/F ratio of an exhaust gas to input a detection signal proportional to the A/F ratio of the exhaust gas to the duty control unit (92).

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 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: 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: A base member mounted to a side of a cylinder block is formed with an inlet-side oil supply passage for supplying an oil to an oil filter, and an outlet-side oil supply passage for discharging the oil from the oil filter. As a result, it is unnecessary to increase the thickness of a wall of the cylinder block or to form a bulged portion in order to form the oil supply passages, thereby contributing to a decrease in weight of the cylinder block. Moreover, because the oil supply passages are formed in the base member, the layouts thereof can be determined freely without restrained by the shape of the cylinder block, thereby contributing an increase in degree of freedom for the design.

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.

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.