Abstract: An outboard motor includes an internal combustion engine provided with a pair of intake valves. The opening and closing operation of one of the intake valves can be paused. The internal combustion engine comprises a vertical crankshaft, a cylinder head provided with an intake port having a pair of intake openings for one combustion chamber, and a fuel injection valve for injecting the fuel into the intake port. The intake port has an upper branch section and a lower branch section extended under the upper branch section. A valve train includes a valve-operation mode changing mechanism. The valve-operation mode changing mechanism pauses the opening and closing operation of the first intake valve and operates the second intake valve for opening and closing the lower intake opening of the lower branch section while the internal combustion engine is operating at engine speeds in a low-speed range.

Abstract: An outboard motor, which is improved for higher output energy, lower fuel consumption, and also simplified in layout of oil paths and facilitating maintenance of hydraulic control valves, includes an engine with a crank shaft, an engine body mounted to a mount case, and a valve driving mechanism for opening and closing intake valves and exhaust valves. The valve driving mechanism includes a valve operating characteristics variable mechanism of an hydraulic type, which changes operating characteristics of the intake and/or exhaust valves in accordance with the revolution speed of the engine. A hydraulic oil path for supplying the valve operating characteristics variable mechanism with hydraulic oil branches from a lubricant oil path for supplying bearing portions of a crank shaft and the valve driving mechanism with lubricant oil.

Abstract: An outboard engine comprises an engine having a crankshaft (36) extending vertically, a flywheel 56 provided on the crankshaft (36) below the engine body, an oil pump (58), and a flywheel chamber (59) defined by a pump body (65) of the oil pump (58) united to coupling walls 61, 62 of the engine body to accommodate the flywheel 56; and a mount case (4) having a support wall 64 for uniting the engine body. The engine body is united with its coupling walls (61, 62) to the support wall (64) via an outer circumferential wall (63) of the pump body (65) such that the coupling walls (61, 62), outer circumferential wall (63) and support wall (64) overlap in the direction of a rotation axis of the crankshaft (36). Such outboard engine permits a connecting portion between the engine body and the mount case, which are united together via the oil pump body, to be decreased in size and weight.

Abstract: It is intended to provide a compact and lightweight outboard engine and to prevent its output loss by preventing or minimizing lubricant oil staying in a crank chamber while the engine is driven in a tilt-up condition. For this purpose, the outboard engine (1) mounted to a boat stern by a mounting device having a tilt shaft comprises an engine (2) including a flywheel (56) positioned at a lower end portion of a vertically extending crankshaft, and an oil pan positioned below the flywheel (56). An upper wall of a flywheel chamber (59) accommodating the flywheel 56 is made up of a bottom wall of a crank chamber made of a crankcase (30), etc., and a bottom wall (30a) of the crankcase (30) forming a front portion of the engine body (3) has a return oil path 71 formed forward of an inner circumferential wall surface (60e) of a circumferential wall (60) of the flywheel chamber (59) and having inflow openings (71a, 71b) through which lubricant oil flows from the crank chamber.

Abstract: It is intended to provide an outboard engine that can be decreased in size and weight by decreasing the size and weight of a connecting portion between an engine body and a mount case that are united together via a pump body of an oil pump. For this purpose, the outboard engine comprises an engine having a crankshaft (36) extending vertically, a flywheel 56 provided on the crankshaft (36) below the engine body, an oil pump (58), and a flywheel chamber (59) defined by a pump body (65) of the oil pump (58) united to coupling walls 61, 62 of the engine body to accommodate the flywheel 56; and a mount case (4) having a support wall 64 for uniting the engine body. The engine body is united with its coupling walls (61, 62) to the support wall (64) via an outer circumferential wall (63) of the pump body (65) such that the coupling walls (61, 62), outer circumferential wall (63) and support wall (64) overlap in the direction of a rotation axis of the crankshaft (36).

Abstract: A box-shaped intake silencer for an engine is obtained by joining together an upper half and a lower half. The intake silencer includes a connecting duct for supplying air to the engine and an intake duct for bringing in outside air. The intake silencer brings in a blow-by gas generated by the engine and returns fresh air purified by a filter to the engine. The filter is inserted into a retaining part made up of the upper and lower halve and held at the retaining pat by joining the upper and lower halves together.

Abstract: An outboard engine assembly having a V-type multi-cylinder engine. A breather chamber is formed in a cam chamber of one row of a V-bank, and an oil separating chamber is formed in a cam chamber of the other row, with the cam chambers of two rows effectively utilized. Both the breather chamber and the oil separating chamber communicate with a crank chamber, with the breather chamber connected to an upstream side of a throttle valve unit. The oil separating chamber is connected to a downstream side of the throttle valve unit via a passage having a PCV valve.

Abstract: An outboard motor (1), which is improved for higher output energy, lower fuel consumption, and also simplified in layout of oil paths and facilitating maintenance of hydraulic control valves, includes an engine (2) that comprises a crank shaft (24), engine body (3) mounted to a mount case (4), and valve driving mechanism (M1) for opening and closing a pair of intake valves (33) and a pair of exhaust valves 34. The valve driving mechanism (M1) includes a valve operating characteristics variable mechanism (M2) of a hydraulic type, which changes operating characteristics of the intake valves 33 in accordance with the revolution speed of the engine. A hydraulic oil path for supplying the valve operating characteristics variable mechanism (M2) with hydraulic oil branches from a lubricant oil path for supplying bearing portions of a crank shaft (24) and the valve driving mechanism (M1) with lubricant oil.