Abstract: An exhaust passage configured to discharge an exhaust gas from an engine of a small watercraft, comprises at least a first exhaust pipe, a second exhaust pipe connected to the first exhaust pipe, and a connecting structure configured to connect the first exhaust pipe and the second exhaust pipe to each other, the connecting structure including a first tubular insertion end portion provided at a connecting end portion of the first exhaust pipe so as to protrude toward a connecting end portion of the second exhaust pipe, a second tubular insertion end portion provided at the connecting end portion of the second exhaust pipe so as to accommodate the first tubular insertion end portion of the first exhaust pipe, a ring groove formed to extend circumferentially over an entire outer peripheral face of the first insertion end portion, and a seal ring configured to engage in the ring groove.

Abstract: A small watercraft comprises a four-cycle engine, an engine speed sensor configured to output a signal according to an engine speed of the engine, first and second hydraulic switches each configured to output a signal according to a pressure of oil, and an electrical control unit configured to control operation of the engine based on signals from the engine speed sensor, and the first and second hydraulic switches. The electrical control unit enters a first detection mode when the engine speed is within a first range, and limits the operation of the engine when detecting that the hydraulic pressure is not more than a first threshold. The electrical control unit enters a second detection mode when the engine speed is within a second range, and causes a notification lamp to be lighted when detecting that the hydraulic pressure is not more than a second threshold.

Abstract: Disclosed is an engine of a personal watercraft having a water jet pump at a rear end thereof, in which a center of gravity of the engine is located rearward for improvement of planing capability of the watercraft. The engine comprises: a crankcase having a front end wall and a rear end wall; a crankshaft provided inside the crankcase; a generator provided at an output end portion of the crankshaft, the generator including a rotor fixed to the crankshaft; a starter motor provided on an output end side of the crankshaft outside the crankcase; and a clutch provided between the starter motor and the rotor of the generator, for connecting/disconnecting the starter motor to/from the rotor.

Abstract: Exhaust outlet equipment provided at a downstream end portion of an exhaust passage of a propulsion engine in a flow of an exhaust gas, wherein the engine is mounted in a small watercraft propelled by a water jet pump. The exhaust outlet equipment typically includes an exhaust pressure reducing chamber provided laterally of a pump room that contains the water jet pump, the chamber having a volume for reducing a pressure of the exhaust gas to a predetermined pressure. The exhaust pressure reducing chamber typically has an introduction port through which the exhaust gas from an exhaust pipe located on an upstream side in the flow of the exhaust gas flows into the exhaust pressure reducing chamber, and a discharge port through which the exhaust gas inside the exhaust pressure reducing chamber is discharged to an ambient side.

Abstract: An oil separator comprises an oil chamber having a first space on an upper side and a second space on a lower side which communicate with each other. An air-fuel mixture transport pipe is connected to a peripheral portion of the oil chamber so as to communicate with the second space. An oil discharge pipe is connected to a lower end portion of the oil chamber. A blow-by gas discharge pipe is connected to an upper end portion of the oil chamber. The second space communicates with the first space so as to inhibit the oil from flowing from the second space into the first space. The first space communicates with the blow-by gas discharge pipe so as to inhibit the oil from flowing from the first space into the blow-by gas discharge pipe. The flow direction at one end portion of the air-fuel mixture transport pipe substantially corresponds with the circumferential direction of the oil chamber.

Abstract: Disclosed is a personal watercraft capable of efficiently placing a dry-sump engine room and of efficiently using a dead space in the engine room. The small dry-sump engine comprises: a plurality of cylinders; at least one cylinder head provided as corresponding to the cylinders; a crankcase chamber; an oil tank chamber independent of the crankcase chamber, the oil tank chamber being located lower than the cylinder head; and an oil return passage configured such that its upper end communicates with the cylinder heads and its lower end communicate with the oil tank chamber.

Abstract: Disclosed is an engine of a personal watercraft capable of preventing water ingress into a penetrating hole for attaching an ignition plug. The engine comprises a cylinder head, a cylinder head cover provided over the cylinder head, an ignition plug attached to the cylinder head, a penetrating hole formed to extend from an upper surface of the cylinder head cover to a lower surface of the cylinder head, for accommodating and attaching the ignition plug inside thereof, a connecting member connected to an upper end of the ignition plug and located inside the penetrating hole, for connecting a power supply to the ignition plug that activates the ignition plug, a closing member for creating a seal between the connecting member and the penetrating hole, and an air hole formed to extend obliquely downward from the penetrating hole so as to communicate with an outside of the cylinder head.

Abstract: Disclosed is a jet-propulsion watercraft having a simple structure for drawing water as cooling water, the inside of which may be cleaned easily. The watercraft typically comprises an engine, a water jet pump driven by the engine, a two-part pump casing, at least one water drawing passage provided so as to communicate with an inside of the water jet pump in a portion where the two parts of the pump casing are connected to each other, and a component cooled by cooling water taken through the water drawing passage.

Abstract: Disclosed is a small watercraft having an engine cooling system which can lessen variation in temperature and temperature distribution of the engine between the time when the engine is starting and when the watercraft is continuously driving with a throttle in a fully open or almost fully open position. The small watercraft adapted to be propelled by a water jet pump driven by an engine, comprises: a first cooling system for cooling a cylinder block of the engine, the first cooling system having an indirect cooling structure; and a second cooling system for cooling an exhaust system, the second cooling system having a direct cooling structure.

Abstract: A first exhaust chamber and a second exhaust chamber are disposed within a body of a watercraft. The first exhaust chamber communicates with an exhaust port of an engine through a first exhaust pipe. A first space of the first exhaust chamber communicates with the second exhaust chamber through a first inverted-U shaped pipe. The second exhaust chamber communicates with another space of the first exhaust chamber through a second inverted-U shaped pipe. The first and second inverted-U shaped pipes are each positioned in the flow path of the exhaust gas and bent to be substantially inverted-U shaped. The other space of the first exhaust chamber communicates with an outside of the body through a second exhaust pipe. An uppermost portion of the first inverted-U shaped pipe and an uppermost portion of the second inverted-U shaped pipe are located higher than a waterline of the watercraft.

Abstract: A personal watercraft including an engine mounted within a body defined by a hull and a deck covering the hull from above is disclosed, the watercraft being configured to cool at least part of the engine and an auxiliary device using water outside the watercraft, the watercraft including a cooling water passage provided in the part of the engine and the auxiliary device, the water outside the watercraft being supplied to the cooling water passage, a coupling member forming a part of a liquid connecting coupler and provided to fluidically communicate with the cooling water passage, the coupling member having a connecting portion to which another coupling member forming another part of the liquid connecting coupler is removably attachable, the coupling member being fixed such that the connecting portion is exposed outside the body, and a lid member configured to open and close the connecting portion of the coupling member.

Abstract: A method and device for processing self-diagnostic information relating to an operating state of a jet-propulsion personal watercraft to display the self-diagnostic information on a display device equipped in the personal watercraft.

Abstract: A jet-propulsion watercraft comprises: an engine; an oil tank provided independently of the engine, for reserving engine oil; and a water jet pump driven by the engine, the water jet pump pressurizing and accelerating water taken in from outside of the watercraft and ejecting the water from the outlet port to propel the watercraft as a reaction of the ejecting water, and the muffler is provided behind the engine and on one of right and left sides of the watercraft and the oil tank is provided behind the engine and on the other side of the watercraft.

Abstract: Disclosed is a personal watercraft capable of preventing oil flow from an engine to a breather device. The personal watercraft comprises: a four-cycle engine; a water jet pump driven by the engine, the water jet pump pressurizing and accelerating water taken in from outside of the watercraft and ejecting the water from the outlet port to propel the watercraft as a reaction of the ejecting water; a breather pipe configured such that a base end is connected to the engine to communicate with an inside of the engine, an intermediate portion is located lower than the base end, and a tip end is located higher than the base end; and a breather box, wherein the tip end of the breather pipe communicates with inside of the breather box and the base end of the breather pipe is located lower than the breather box.

Abstract: A water-jet propulsion personal watercraft is disclosed. The personal watercraft typically includes a body including a hull and a deck covering the deck from above, a water jet pump configured to propel the watercraft and including a pump shaft extending in a longitudinal direction of the body, a V-type four-cycle engine mounted within the body and configured to drive the water jet pump, wherein the engine includes a crankshaft, an output shaft extending in a direction substantially perpendicular to the crankshaft and connected to the pump shaft, the output shaft being configured to output rotation transmitted from the crankshaft to outside the engine, and a rotation transmission system configured to transmit the rotation of the crankshaft to the output shaft, wherein the engine is mounted within the body in such a manner that the crankshaft extends in a width direction of the body.

Abstract: A stand-up type personal watercraft comprises a body including a hull and a deck covering the hull from above, the body having a foot deck at a rear portion of the deck, on which an operator rides, a water jet pump configured to propel the watercraft, and a four-cycle multi-cylinder engine provided within the body and configured to drive the water jet pump, wherein the engine is disposed forward of the foot deck within the body and substantially at a center position in a longitudinal direction of the body.

Abstract: Disclosed is a small watercraft having an engine cooling system which can lessen a temperature distribution of an engine. The small watercraft comprises an engine for driving a propulsion unit of the watercraft, and the engine includes a first cooling passage formed inside a cylinder head of the engine, for cooling the cylinder head with a coolant flowing therethrough, and a second cooling passage formed inside a cylinder block of the engine, for cooling the cylinder block of the engine with a coolant flowing therethrough, the first and second cooling passages being independent of each other.

Abstract: A personal watercraft including an engine mounted within a body defined by a hull and a deck covering the hull from above is disclosed, the watercraft being configured to cool at least part of the engine and an auxiliary device using water outside the watercraft, the watercraft including a cooling water passage provided in the part of the engine and the auxiliary device, the water outside the watercraft being supplied to the cooling water passage, a coupling member forming a part of a liquid connecting coupler and provided to fluidically communicate with the cooling water passage, the coupling member having a connecting portion to which another coupling member forming another part of the liquid connecting coupler is removably attachable, the coupling member being fixed such that the connecting portion is exposed outside the body, and a lid member configured to open and close the connecting portion of the coupling member.

Abstract: An exhaust system for a small watercraft is disclosed, wherein the exhaust system includes an exhaust chamber having a predetermined volume, within which an exhaust gas discharged from an engine flows, the exhaust gas containing water supplied at a position of the exhaust system, and an exhaust pipe having an upstream end portion in a flow passage of the exhaust gas, which is connected to the exhaust chamber, the exhaust pipe being configured to discharge the exhaust gas from the exhaust chamber, wherein the upstream end portion of the exhaust pipe is configured to protrude into the exhaust chamber to a vicinity of a lower end of the exhaust chamber and has an upstream opening end face that opens substantially downward so as to be spaced apart a predetermined distance from an inner surface of the exhaust chamber, which is opposed to upstream opening end face.

Abstract: Disclosed is a jet-propulsion personal watercraft adapted to eject water pressurized and accelerated by a water jet pump from an outlet port so as to be propelled as the resulting reaction, the personal watercraft being provided with a cruising control switch to allow an electric control unit to control a throttle actuator in accordance with an operation of the cruising control switch so that the watercraft cruises at a predetermined cruising speed or engine speed.