Abstract: A small boat includes engines mounted on a hull, a plurality of water jet propulsion units disposed on both sides of a longitudinal axis of the hull and driven by the engines, and a steering wheel arranged to change jet directions of the water jet propulsion units. The small boat further includes a steering angle sensor arranged to detect a rotational angle of the steering wheel, front and rear gravity sensors arranged to detect a turning state of the hull, and a control device to which the rotational angle and the turning state of the hull are inputted in order to control thrusts of the water jet propulsion units such that the turning state coincides with any one of a group of target steady turning radii corresponding to the rotational angle of the steering wheel. The small boat turns along the steady radius regardless of any water conditions.

Abstract: A watercraft includes an engine output control device that can adjust the maximum output of the engine. The output device can be constructed of mechanical devices for adjusting the relationship between the movement of a throttle lever and a throttle valve, an electronic device for proportionally controlling the position of throttle valves in relation to the movement of the throttle lever, are other devices for controlling engine speeds in other ways.

Abstract: A watercraft includes an engine output control device that can adjust the maximum output of the engine. The output device can be constructed of mechanical devices for adjusting the relationship between the movement of a throttle lever and a throttle valve, an electronic device for proportionally controlling the position of throttle valves in relation to the movement of the throttle lever, are other devices for controlling engine speeds in other ways.

Abstract: A watercraft has an exhaust system. The exhaust system has a first portion cooled by cooling jackets and a second portion cooled by merged flow. The first portion is coupled to the second portion with a flexible coupling having an undulating surface. An overheat detection system is positioned proximate the flexible coupling. The overheat detection system is arranged to detect a rapid increase in temperature resulting from a blocked cooling jacket. During periods of normal operation, a first temperature reading is detected. During periods of abnormal operation, a rapid increase in temperature indicates a sudden decrease in cooling water within the cooling jacket. Warning signals are emitted to the operator by an overheat prevention unit to advise the operator of the condition.

Abstract: A watercraft has an exhaust system. The exhaust system has a first portion cooled by cooling jackets and a second portion cooled by merged flow. The first portion is coupled to the second portion with a flexible coupling having an undulating surface. An overheat detection system is positioned proximate the flexible coupling. The overheat detection system is arranged to detect a rapid increase in temperature resulting from a blocked cooling jacket. During periods of normal operation, a first temperature reading is detected. During periods of abnormal operation, a rapid increase in temperature indicates a sudden decrease in cooling water within the cooling jacket. Warning signals are emitted to the operator by an overheat prevention unit to advise the operator of the condition.

Abstract: An engine for a watercraft includes a cooling system having a coolant supply. The coolant supply supplies an engine coolant jacket with a flow of coolant that is controlled by a temperature dependent flow control valve. The coolant supply also supplies an exhaust conduit coolant jacket independently of the engine coolant jacket.

Abstract: A number of embodiments of induction systems for watercraft that employ, in addition to the plenum chamber of the air inlet device for the induction system, a further plenum chamber of a predetermined volume that communicates with the induction system plenum chamber for providing silencing and/or tuning effects to improve induction efficiency and silencing. In addition there are disclosed compact intake devices that incorporate plenum chambers for this purpose.

Abstract: A watercraft includes an improved seat design that allows a rider to better absorb impact shocks with his or her legs as the watercraft bounds over wakes. The seat assembly includes a front seat section and a rear seat section that is sized to accommodate one or more riders in tandem with each rider straddling the seat. The front seat section is narrower than the rear seat section to permit the front rider to place his or her legs more directly in front of him or her. This position improves the rider's comfort and allows the rider to assume a stance in which the rider can better absorb impact shocks on the watercraft. In order to accommodate this seat design, an improved engine component layout is provided so as to reduce the width of the upper end of the engine. The induction and exhaust systems of the engine are laid out on the lower sides of the watercraft, and extend at least partially beneath foot wells that flank the sides of the seat assembly.

Abstract: Several embodiments of personal watercraft having very compact construction, in particularly embodying a compact propulsion system wherein the engine and a number of its accessories all define a very compact area. A balance shaft is driven by the engine crankshaft for reducing the transmission of vibrations to the watercraft riders.

Abstract: A watercraft includes a monitoring and control system to sense the operational state of a catalytic device and a cooling system used with an exhaust system of the watercraft. The monitoring and control system includes a collection port formed downstream of the catalytic device. During diagnostic testing of the engine and the catalytic device, a collection element is inserted into the collection port. A plug, however, normally closes the collection port during normal engine operation. A cover extends over the collection port and a substantial portion of the surrounding exhaust pipe. The cover, or at least a portion thereof, is readily removable so as to provide access to the collection port. The exhaust system also includes a water trap located downstream of the collection port. A foam core support member supports the water trap within a hull of the watercraft, with an insulator positioned between the support member and the water trap.

Abstract: An air supply conduit system for a watercraft having an air breathing internal combustion engine within the watercraft interior includes at least one air supply conduit extending from an outlet end located in the watercraft interior to an inlet end located outside the watercraft. A noise suppressing resonating chamber connected to the air supply conduit damps noise from the internal combustion engine from the outlet end of the conduit towards the inlet end thereof. The air supply conduit may be positioned within the watercraft to minimize entrapment of liquid within the conduit and the noise suppressing resonating chamber. An inlet fitting including a noise suppressor is located at the inlet end of the conduit.

Abstract: Several embodiments of personal watercraft having very compact construction, in particularly embodying a compact propulsion system wherein the engine and a number of its accessories all define a very compact area. This permits the center of gravity to be located at the desired location and maintain good balance for the watercraft regardless of the number of passengers who occupy it.

Abstract: A personal watercraft catalytic exhaust system wherein an over-temperature sensor is provided that is effective to shut down the engine in the event the catalyst reaches a dangerous temperature. The engine, once shutdown, cannot be restarted until the temperature falls below a predetermined temperature which may be lower than the overheat temperature. In the process of stopping the engine, it is slowed down first so as to give the rider additional warning that the shutdown procedure will be initiated.

Abstract: A lubrication system for the internal combustion engine of a motorcycle that includes a pump that outputs a constant amount of fluid per cycle of operation and a delivery valve which selectively passes lubricant to the engine or returns lubricant back to the system to vary the amount of lubricant supplied by the lubricant pump. The system is designed so as to self purge air from the system by mounting the lubricant pump and the delivery valve in close proximity to each other and at a lower level than the lubricant storage tank. In addition, the engine is supplied with lubricant from the supply outlet through a conduit that terminates at a point higher than the supply outlet so as to preclude lubricant from draining into the engine when the engine is not running.

Abstract: A lubrication system for the internal combustion engine of a motorcycle that includes a pump that outputs a constant amount of fluid per cycle of operation and a delivery valve which selectively passes lubricant to the engine or returns lubricant back to the system to vary the amount of lubricant supplied by the lubricant pump. The system is designed so as to self purge air from the system by mounting the lubricant pump and the delivery valve in close proximity to each other and at a lower level than the lubricant storage tank. In addition, the engine is supplied with lubricant from the supply outlet through a conduit that terminates at a point higher than the supply outlet so as to preclude lubricant from draining into the engine when the engine is not running.