Abstract: A crankshaft has a helical drive gear formed as one of the crank webs at an end portion thereof. Another crank web outside of the drive gear is made in two parts, an integral balance weight mounting portion and a removable balance weight. In one embodiment, a crankshaft 12 features a crankshaft body 33 including a gear 24 for outputting rotation formed on one side of a crankpin 17d. The crankshaft also includes a first balance weight mounting portion 30g formed on the other side of the crankpin 17d and a first balance weight 31g to be mounted to the first balance weight mounting portion 30g. The crankshaft body 33 may be formed with a second balance weight mounting portion 30a separately from the first balance weight mounting portion 30g, and a second balance weight 31 a mounted to the second balance weight mounting portion.

Abstract: An oil jet device for piston cooling in which no press-fitting device is required, and the O-ring is prevented from being broken. A filter plug is inserted into an oil passage opening from the crank journal of a crankcase toward the side of the lower portion of the cylinder, and the crank journal is sealed by a plain bearing being abutted against the filter plug. The oil passage is formed by ring-shaped feed paths formed in the ring-shape on the bearing portions on the plain bearing and the crankcase.

Abstract: An oil tank system for an engine capable of reducing the overall height of an engine is disclosed. Breather chambers of a dry sump type engine in which an oil tank for storing engine oil is provided independently from the engine are defined in an oil tank. The breather chambers and are in communication with the engine and a breather chamber section is partially partitioned into the first breather chamber and the second breather chamber with a gasket. An oil sump portion for accumulating oil during period of turn-over of a watercraft is formed in the first breather chamber. An oil return passage provided in the first breather chamber forms a breathing passage during a turn-over condition of the watercraft. A sump portion for oil which counter flows in the return passage during a turn-over condition of the watercraft is provided in an upper portion (lower portion during a turn-over condition) of the second breather chamber.

Abstract: A sensor arrangement structure for an engine for a personal watercraft for preventing an engine controlling sensor from being splashed with water so that the engine operates appropriately. An engine for driving a jet propulsion pump is provided in a watercraft body surrounded by a hull and a deck with a throttle body and a surge tank contiguous to the throttle body being provided on the intake side of the engine and forming a horizontal partition assembly A extending in a forward and rearward direction and extending in a substantially horizontal direction at an upper portion of the engine. A sensor for controlling the engine is disposed above the horizontal partition assembly. An intercooler is disposed just below the surge tank. The intake pressure sensor for detecting the intake pressure on the downstream side with respect to the throttle valve is disposed adjacent to a head cover and is attached in a state wherein it is spaced away from an upper face of the throttle body.

Abstract: To utilize a small space in a vessel body efficiently and simultaneously augment the output power and realize a suitable water supply structure to an intercooler. A surge tank and an intercooler are provided between a supercharger and an internal combustion engine incorporated in the inside of a vessel body. The intercooler is disposed just below the surge tank, and an intake entrance from the supercharger and an exit to the surge tank are provided above the intercooler. A jet pump and the intercooler are in communication with each other directly by a cooling water hose, and cooling water is supplied from the intake entrance side into the intercooler.

Abstract: A mounting face of an oil pan is provided in the vicinity of the outside of a fastening bolt for fastening un upper case and a lower case of an engine that support a crankshaft when viewed from the bottom. A strainer is provided in the vicinity of the engaging surface between the oil pan and the engine along the engaging surface. An oil pump is provided at the end of the crankshaft. An oil exit in communication with the oil pump is provided on the oil pan at the end in the axial direction of the crankshaft and is brought into communication with the oil pump by the joint pipe. The aforementioned arrangement provides a dry-sump engine for a small planing boat that can reduce the overall height and size of the engine.

Abstract: To provide a system for lubricating an engine for a personal watercraft, which is capable of simplifying an oil piping structure. An oil pump driven by a crankshaft of an engine and a relief valve for controlling a discharge pressure of the oil pump are provided in an oil tank provided on an extension of the crankshaft of the engine. Suction/discharge passages and the like for the oil pump are provided integrally with a tank main body. An oil filter in communication with the oil pump is provided in an upper portion of the oil tank, and communication passages for the oil filter are provided integrally with the oil tank. The oil filter is aligned with an opening of a deck. The tank main body covers drive chambers for accessories such as an ACG, a balancer shaft, and a starter motor of the engine.

Abstract: To provide an output shaft structure of a personal watercraft, which is capable of enhancing the durability of the engine. An engine is mounted on a watercraft body with a crankshaft extending in the longitudinal direction of the watercraft body. A shaft of a propulsion device is coupled to a rear end of the crankshaft in such a manner as to be disposed on an extension of the crankshaft. The crankshaft is supported by an engine case via plain metal. An output shaft is provided separately from the crankshaft and is coupled to the rear end of the crankshaft. The shaft of the propulsion device is coupled to the rear end of the output shaft. The output shaft is supported by the engine case via rolling bearings immovable in a thrust direction. A spline is formed on or in each of the rear end of the crankshaft and the front end of the output shaft, and a spline to be engaged with these splines is formed in or on an inner surface of a connection pipe.

Abstract: To provide an output power shaft structure for a personal watercraft which is superior in durability. A shaft of a propulsion device is connected to a rear end of a crankshaft of an engine, which is carried on a watercraft body such that the crankshaft thereof is directed in a longitudinal direction of the watercraft body, on an extension line of the crankshaft. A rear end of the crankshaft is disposed in an engine case, and an output power shaft separate from the crankshaft is connected to the rear end of the crankshaft. The shaft of the propulsion device is connected to a rear end of the output power shaft. The rear end of the crankshaft and a front end of the output power shaft are connected to each other in a transmission chamber in which a transmission mechanism for transmitting power of the crankshaft to a camshaft is provided at a rear portion of the crankshaft. A driving sprocket wheel of the transmission mechanism is provided on the output power shaft.

Abstract: An engine mount structure for a personal watercraft allows the engine to be incorporated in an inclined well-balanced state in the watercraft body having a hull and a deck, while making efficient use of the space within the body. The engine for driving a jet propulsion pump has an upper case and a lower case joined along a transverse plane parallel to the engine crankshaft and is mounted in the body so as to be inclined about the crankshaft, whereby an intake port side of the engine faces obliquely upwardly. Mounts on upwardly facing intake side of the engine are provided on the lower case, while mounts on the downwardly facing exhaust side are provided on the upper case. A starter motor is attached to the upwardly facing side of the engine.

Abstract: A personal watercraft having an engine provided in a body formed from a hull and a deck, and a supercharger provided for the engine. An oil exit of the supercharger is disposed higher than an oil surface in the oil pan when the engine is not running. An oil tank is provided on an extension line of a crankshaft. A one-way valve is interposed in an oil returning passage, which communicates with the oil exit of the supercharger. This configuration minimizes oil residing in the supercharger when an engine is not running, and thus reduces the degradation of the entire oil supply for the engine and supercharger.

Abstract: An engine suitable for mounting in a small planing boat, which both lowers the center of the gravity of the boat, and enables a degree of freedom in arranging accessories. Balancers are arranged on the left and on the right of a crankshaft on a parting face of an engine. The engine is mounted in the body of the small planing boat surrounded by a hull and a deck. A starter motor and an idle gear of one balancer are arranged on the side opposite the starter motor, with the crankshaft between them. Also disposed between the idle gear and the starter motor is a cylinder. An oil tank is provided at the front of the engine, and two oil supply passages leading to the balancer supports are formed in the case of the oil tank.

Abstract: To provide a supercharger cooling structure for a small watercraft which can sufficiently cool the supercharger. In a small watercraft in which an engine with a supercharger is incorporated, cooling water from a jet pump is supplied to the supercharger through a different supercharger cooling water passage independent of any other cooling water passage. The cooling water from the supercharger cooling water passage is first supplied to the supercharger to cool the supercharger and then supplied to an exhaust system provided on the downstream with respect to the supercharger in an exhaust system for the engine, whereafter it is discharged to the outside of the watercraft together with exhaust gas. Oil is supplied to the supercharger for lubrication of a bearing portion of the supercharger and is supplied to an oil jacket formed in a bearing casing to cool the bearing casing.

Abstract: To augment the durability of a turbocharger. A hull and a deck of a personal watercraft are formed watertight and an opening of the deck is closed with a seat to form a body internal space. An intake duct for introducing atmospheric air from outside the body is provided in the space. An engine and a turbocharger connected to an exhaust manifold of the engine are provided in the space and the turbocharger is disposed higher than a body internal opening of the intake duct. A water jacket is formed in a casing of a turbine portion of the turbocharger and an oil jacket is formed in a bearing casing of the turbocharger, and cooling water is supplied to the water jacket and cooling oil is supplied to the oil jacket. The cooling water to the water jacket is supplied by a different turbocharger cooling water passage independent of any other cooling water passage.

Abstract: A personal watercraft with an engine and a supercharger, in which a speedy, positive operation of the supercharger is ensured. The system includes an engine for driving a jet propelling pump provided in a watercraft body formed by a hull and a deck in such a manner as to extend in a length direction of the watercraft body. An oil pump is provided on the front side of the engine and a supercharger 140 is provided on the rear side of the engine. The supercharger and an end portion of a main gallery communicate with each other via an oil supply pipe. Oil supplied to the supercharger is used for lubricating a bearing portion of the supercharger. Further, the oil is supplied to an oil jacket formed in a bearing casing of the supercharger to cool the bearing casing. A one-way valve is interposed in an oil return pipe which communicates to an oil outlet of the supercharger.

Abstract: In order to provide an intercooler assuming a simple structure that enables cooling of supercharging air and absorption of any expansion/contraction of the cooling water pipe and the casing attributable to the heat of the supercharging air, intake/outlet pipes of a heat exchanger housed inside a cooling space formed within a case are inserted at cylindrical pipe insertion portions formed at the case, and any gap present between the intake/outlet pipes and the insertion portions are sealed by seal members each constituted of an elastic material formed in a staged cylindrical shape having a first cylindrical portion placed in complete contact with one of the pipe insertion portions and a second cylindrical portion placed in complete contact with either one of the intake/outlet pipes, which are also utilized to fit the heat exchanger in the case with a gap.

Abstract: To prevent the dispersal of water in a watercraft body, prevent interference of a coupler with piping, and prevent deterioration of the piping. An engine is mounted on a watercraft body with a crankshaft of the engine extending along the longitudinal direction of the watercraft body and a shaft of a jet pump is coupled via a coupler to a rear end of the crankshaft in such a manner so as to be disposed on an extension of the crankshaft. A coupler cover is provided for covering the coupler, and piping for cooling water, which is in communication with the jet pump, is fixed onto the coupler cover. A turbo-charger is disposed over the coupler, and the piping is fixed on the coupler cover at a position between the coupler cover and the turbo-charger. The coupler cover is turnable around the shaft.

Abstract: An oil tank system for an engine capable of reducing the overall height of an engine is disclosed. Breather chambers of a dry sump type engine in which an oil tank for storing engine oil is provided independently from the engine are defined in an oil tank. The breather chambers and are in communication with the engine and a breather chamber section is partially partitioned into the first breather chamber and the second breather chamber with a gasket. An oil sump portion for accumulating oil during period of turn-over of a watercraft is formed in the first breather chamber. An oil return passage provided in the first breather chamber forms a breathing passage during a turn-over condition of the watercraft. A sump portion for oil which counter flows in the return passage during a turn-over condition of the watercraft is provided in an upper portion (lower portion during a turn-over condition) of the second breather chamber.

Abstract: To prevent the dispersal of water in a watercraft body, prevent interference of a coupler with piping, and prevent deterioration of the piping. An engine is mounted on a watercraft body with a crankshaft of the engine extending along the longitudinal direction of the watercraft body and a shaft of a jet pump is coupled via a coupler to a rear end of the crankshaft in such a manner so as to be disposed on an extension of the crankshaft. A coupler cover is provided for covering the coupler, and piping for cooling water, which is in communication with the jet pump, is fixed onto the coupler cover. A turbo-charger is disposed over the coupler, and the piping is fixed on the coupler cover at a position between the coupler cover and the turbo-charger. The coupler cover is turnable around the shaft.

Abstract: A sensor arrangement structure for an engine for a personal watercraft for preventing an engine controlling sensor from being splashed with water so that the engine operates appropriately. An engine for driving a jet propulsion pump is provided in a watercraft body surrounded by a hull and a deck with a throttle body and a surge tank contiguous to the throttle body being provided on the intake side of the engine and forming a horizontal partition assembly A extending in a forward and rearward direction and extending in a substantially horizontal direction at an upper portion of the engine. A sensor for controlling the engine is disposed above the horizontal partition assembly. An intercooler is disposed just below the surge tank. The intake pressure sensor for detecting the intake pressure on the downstream side with respect to the throttle valve is disposed adjacent to a head cover and is attached in a state wherein it is spaced away from an upper face of the throttle body.