Abstract: A water jet propulsion watercraft includes a hull having a sealed engine room, an engine installed in the engine room, a jet propulsion unit arranged to be driven by the engine so as to suck in water from around the hull and jet the water, a saddle type seat disposed above the engine room, a first exhaust pipe, an exhaust pipe cooling unit, and a catalyst unit. The first exhaust pipe is attached to a side of the engine inside the engine room, extends rearward from the side of the engine, and is arranged to guide exhaust gas discharged from the engine. The exhaust pipe cooling unit is arranged to cool the first exhaust pipe. The catalyst unit is connected to the first exhaust pipe, is disposed inside the engine room so as to oppose a rear surface of the engine, and is arranged to promote reaction of components contained in the exhaust gas.

Abstract: A water jet propulsion boat includes a fuel pump driven by an electric control unit and arranged to deliver fuel from a fuel tank to an engine via a fuel pipe, and a fuel pressure sensor arranged to detect a pressure of the fuel delivered to the engine by the fuel pump. When a magnitude of the fuel pressure detected by the fuel pressure sensor is less than a predetermined magnitude, the fuel pump is activated. On the other hand, when the magnitude of the fuel pressure detected by the fuel pressure sensor is equal to or greater than the predetermined magnitude, the fuel pump is deactivated. Also, when the fuel pressure detected by the fuel pressure sensor becomes equal to or less than an abnormal threshold value, either one or both of the fuel pump and the engine are deactivated. The water jet propulsion boat lowers power consumption, reduces battery size, extends battery life, and lowers costs.

Abstract: A boat includes a connection structure that connects couplings via a transfer shaft on a rear end portion of a crankshaft extending rearward from an engine. The crankshaft and the transfer shaft are connected by screwing an external thread and a front internal thread, and the transfer shaft and the couplings are connected by screwing an external thread and an internal thread. There are provided an inner bolt that strengthens the connection between the external thread and the front internal thread, an end bolt that strengthens the connection between the transfer shaft and the couplings, and an outer nut that strengthens the connection between the crankshaft and the transfer shaft. The boat can prevent movement between the crankshaft and an intermediate member and between the intermediate member and a coupling both in a rotational direction and in an axial direction without causing an increase of processing time or processing cost.

Abstract: A misfire detecting device is provided for a water jet propulsion watercraft in which a propulsion unit operates through an operation of an engine to propel the water jet propulsion watercraft. The misfire detecting device includes injectors arranged to inject fuel into the engine under a fuel injection amount adjusting control implemented by an electric control device, ignition plugs arranged to ignite the fuel injected into the engine from the injectors to operate the engine, an oxygen sensor arranged to detect that a misfire occurs in the engine, a warning lamp and buzzer arranged to inform that the misfire occurs, etc. The misfire detecting device prevents the warning lamp and the buzzer from informing the warning if the misfire is caused through the control by the electric control device.

Abstract: A water jet propulsion boat includes a fuel pump driven by an electric control unit and arranged to deliver fuel from a fuel tank to an engine via a fuel pipe, and a fuel pressure sensor arranged to detect a pressure of the fuel delivered to the engine by the fuel pump. When a magnitude of the fuel pressure detected by the fuel pressure sensor is less than a predetermined magnitude, the fuel pump is activated. On the other hand, when the magnitude of the fuel pressure detected by the fuel pressure sensor is equal to or greater than the predetermined magnitude, the fuel pump is deactivated. Also, when the fuel pressure detected by the fuel pressure sensor becomes equal to or less than an abnormal threshold value, either one or both of the fuel pump and the engine are deactivated. The water jet propulsion boat lowers power consumption, reduces battery size, extends battery life, and lowers costs.

Abstract: An abnormality detection device of a fuel pump reduces costs and prevents detection error or breakdown by making the fuel pressure sensor unnecessary. The abnormality detection device includes an abnormality detection circuit, a fuel pump driving voltage detection unit to detect the voltage value of an abnormality detection circuit, and a meter. The abnormality detection circuit is constituted by the circuit including a resistance disposed between a battery side of the fuel pump motor to drive the fuel pump and a ground side. If the voltage value detected by the fuel pump driving voltage detection unit is larger than the upper limit or lower than the lower limit of the normal range, the warning lamp of the meter flashes and a buzzer makes an alarm sound. The abnormality detection circuit is housed in the fuel pump module disposed in the fuel tank.

Abstract: A water jet propulsion boat is constructed such that a fuel pressure detection device is free from a detection error or breakdown and a restart ability of an engine is protected against malfunction. A fuel tank is provided in a boat body of the water jet propulsion boat through vibration absorbing members. A fuel pump unit including a fuel pump is provided in the fuel tank. A fuel pressure sensor is provided in the fuel pump unit. An electric control device stops the fuel pump if the value detected by the fuel pressure sensor is out of the normal value range. Additionally, an electric control device stops operation of the fuel pump if the fall sensor detects the overturning of the boat body and if the detected value of the fuel pressure sensor is out of the normal value range. A regulator and a filter are provided to the fuel pump unit.

Abstract: A supercharger can have a lubrication system that includes a speed increasing mechanism, accommodated in a second housing, for increasing the rotation speed of a drive shaft and transmitting the increased rotation speed to a rotary shaft. An oil sump can be configured to for hold lubricant oil for lubricating the speed increasing mechanism. A pump mechanism can be driven by the rotation of the drive shaft to supply the lubricant oil held in the oil sump to the speed increasing mechanism, in which the pump mechanism is constituted with a screw pump made up of a screw provided on the drive shaft. A pump chamber can rotatably support the drive shaft and accommodate the screw. An oil introduction hole and an oil introduction tube can connect the oil sump and the interior of the pump chamber, and a gap can be formed between the screw and the pump chamber.

Abstract: An intake system for a supercharged engine can include a blow-off passage provides communication between the upstream side of the throttle valve and the upstream side of a supercharger. A blow-off valve opens and closes the blow-off passage. The blow-off valve can be configured to open and close based upon pressure on the downstream side of the throttle valve. The present intake system can further comprise a first conduit providing communication between the upstream side of the throttle valve and the blow-off valve, a second conduit providing communication between the downstream side of the throttle valve and the blow-off valve, and a solenoid valve for switching between the first and second conduits.

Abstract: A watercraft can include an engine having a crankshaft with its output end extending rearward of a crankcase and a supercharger for compressing air feeding it to the engine. The supercharger can be located forward of a rear end of the crankcase. An exhaust pipe, designed to discharge combustion gas out of the watercraft, can be disposed above the supercharger. Forward of the supercharger, an intake box having an intake duct can be provided. An intercooler can be located beside the supercharger, through which the supercharger feeds the compressed air toward the engine.

Abstract: A supercharger can have a lubrication system that includes a speed increasing mechanism, accommodated in a second housing, for increasing the rotation speed of a drive shaft and transmitting the increased rotation speed to a rotary shaft. An oil sump can be configured to for hold lubricant oil for lubricating the speed increasing mechanism. A pump mechanism can be driven by the rotation of the drive shaft to supply the lubricant oil held in the oil sump to the speed increasing mechanism, in which the pump mechanism is constituted with a screw pump made up of a screw provided on the drive shaft. A pump chamber can rotatably support the drive shaft and accommodate the screw. An oil introduction hole and an oil introduction tube can connect the oil sump and the interior of the pump chamber, and a gap can be formed between the screw and the pump chamber.

Abstract: A supercharger can have a lubrication system that includes a speed increasing mechanism, accommodated in a second housing, for increasing the rotation speed of a drive shaft and transmitting the increased rotation speed to a rotary shaft. An oil sump can be configured to for hold lubricant oil for lubricating the speed increasing mechanism. A pump mechanism can be driven by the rotation of the drive shaft to supply the lubricant oil held in the oil sump to the speed increasing mechanism, in which the pump mechanism is constituted with a screw pump made up of a screw provided on the drive shaft. A pump chamber can rotatably support the drive shaft and accommodate the screw. An oil introduction hole and an oil introduction tube can connect the oil sump and the interior of the pump chamber, and a gap can be formed between the screw and the pump chamber.

Abstract: An exhaust gas sensor inhibits a detecting part of an exhaust gas sensor from being exposed to water and has high detection accuracy and high durability. The exhaust gas sensor has a sensor body and a protective cover. The sensor body has an outer housing. The outer housing has a plurality of gas inlets. A gas detection element for detecting a component of the exhaust gas (e.g., oxygen) disposed within the outer housing. The protective cover has a cylindrical shape and has a plurality of protrusions at its opposing ends. The protrusions provide a tight fit with the outer housing. The protective cover is attached to the outer periphery of the outer housing without closing gas inlets formed through the outer cylinder by press-fitting the outer cylinder into the protective cover.

Abstract: An intake system for a supercharged engine capable of improving acceleration performance by improving engine response during acceleration. In one embodiment, a planing boat includes an intake passage provided with a supercharger and a throttle valve. A blow-off passage provides communication between the upstream side of the throttle valve and the upstream side of a supercharger. A blow-off valve opens and closes the blow-off passage. The intake system can further comprises a throttle sensor. The blow-off valve can be configured to open and close based upon pressure on the downstream side of the throttle valve. For example, the blow-off valve can be closed when a detection value from the throttle sensor exceeds a preset rate-of-change value ?0.

Abstract: A watercraft can include an engine connected to multi-furcated intake passages and multi-furcated exhaust passages. The engine can have a crankshaft with its end extending rearwardly of the crankcase. The engine can also have a supercharger and an intercooler. The intercooler and the supercharger can be located forward of the crankcase. An exhaust pipe, designed to discharge combustion gas out of a body through multi-furcated exhaust pipes, is disposed above the supercharger. Forward of the supercharger is located an intake box, on the upper surface of which an intake duct is provided. The intercooler can be located beside the supercharger, through which the supercharger feeds the compressed air toward the engine.

Abstract: A watercraft can include an engine having a crankshaft with its output end extending rearward of a crankcase and a supercharger for compressing air feeding it to the engine. The supercharger can be located forward of a rear end of the crankcase. An exhaust pipe, designed to discharge combustion gas out of the watercraft, can be disposed above the supercharger. Forward of the supercharger, an intake box having an intake duct can be provided. An intercooler can be located beside the supercharger, through which the supercharger feeds the compressed air toward the engine.

Abstract: An engine has a charging system in which pressurized air is supplied to an intake side of the engine through an intake air passage. An induction passage branches and extends from the middle of the intake air passage and is provided with a control valve. The induction passage is in communication with an exhaust passage. The induction passage supplies secondary air to the exhaust passage through the control valve to treat the engine's exhaust gas.

Abstract: A small watercraft includes a hull, an internal combustion engine and an engine speed limiting arrangement. The hull defines an engine compartment in which the engine is supported. The engine speed limiting arrangement comprises an engine condition sensor and an electronic control unit that is operatively connected to the engine condition sensor. The engine speed limiting arrangement is configured to regulate the engine speed of the engine such that the engine speed remains between a maximum value above which the engine can be damaged and a minimum value below which the watercraft will no longer stay in a planing state. Methods for operating the engine speed limiting arrangement are also disclosed.

Abstract: A watercraft includes an improved engine control system that enhances the responsiveness of the watercraft and eases watercraft operation. The watercraft includes a propulsion device, such as a jet propulsion unit, and an engine that powers the propulsion device. The engine control system is configured to maintain or increase engine speed under certain operating conditions.

Abstract: A small watercraft includes a hull, an internal combustion engine and an engine speed limiting arrangement. The hull defines an engine compartment in which the engine is supported. The engine speed limiting arrangement comprises an engine condition sensor and an electronic control unit that is operatively connected to the engine condition sensor. The engine speed limiting arrangement is configured to regulate the engine speed of the engine such that the engine speed remains between a maximum value above which the engine can be damaged and a minimum value below which the watercraft will no longer stay in a planing state. Methods for operating the engine speed limiting arrangement are also disclosed.