Abstract: A cooling system for an outboard motor includes an improved construction that can inhibit a housing unit of the outboard motor from absorbing heat that causes discoloring of the unit. The outboard motor includes a power head that has an engine. The housing unit depends from the power head. An exhaust conduit is arranged to discharge exhaust gases from the engine. At least a portion of the exhaust conduit extends through the housing unit. A cooling system is arranged to cool at least the portion of the exhaust conduit by coolant. The cooling system includes an inner coolant pool surrounding the portion of the exhaust conduit and an outer coolant pool surrounding the inner coolant pool. The cooling system supplies the coolant to the inner and outer pools. The coolant supplied to the outer pool is cooler than the coolant supplied to the inner pool.

Abstract: A piston ring comprises a plurality of recesses that are formed in its outer peripheral edge. The recesses have any of a number of profiles such as semicircular, chordal, arcuate, and triangular. The piston ring controls the passage of lubricant between a region defined between the piston ring and an upper compression sealing ring. The recesses can be positioned to pass over an exhaust port formed in a cylinder wall or to pass over other regions of the cylinder wall. By passing over the exhaust port, the piston ring better accommodates fluctuations in dimensions that are induced by temperature changes by passing over other regions of the cylinder wall, the piston ring enhances the distribution of lubricant, especially in cylinders having a generally horizontal or inclined center axis.

Abstract: A valve cam mechanism for a four-cycle engine includes an improved construction. The engine includes at least one camshaft having cam lobes to activate at least one of an intake valve and an exhaust valve. The camshaft defines an aperture next to at least one of the cam lobes. The aperture extends generally normal to an axis of the camshaft. A decompression mechanism is provided for manual starting of the engine. The decompression mechanism includes a shaft extending through the aperture. An actuator is affixed to the shaft for pivotal movement about an axis of the shaft. The actuator has a first section arranged to hold the intake or exhaust valve in an open position when the actuator exists in an initial position. A second section is arranged to initially retain the actuator in the initial position and to release the actuator from the initial position when the camshaft rotates. The shaft is rigidly supported by an inner surface of the aperture in part.

Abstract: A four-cycle engine includes a cylinder block defining a cylinder bore. A piston is reciprocally disposed within the cylinder bore. A cylinder head member closes an end of the cylinder bore to define a combustion chamber together with the cylinder bore and the piston. The cylinder head member defines an inner passage having a first end communicating with the combustion chamber and a second end terminating at an outer surface of the cylinder head. A valve assembly having a valve section and an actuateable section is provided. The valve section is selectively placed at an open position and a closed position to connect and disconnect the inner passage with the combustion chamber, respectively. The actuateable section is formed oppositely from the valve section. A valve actuation mechanism is arranged to actuate the actuateable section to move the valve section between the open position and the closed position.

Abstract: A charging system for a plurality of batteries is provided to better regulate the charging process of the batteries, particularly in the case where one of the batteries is being charged by multiple generators. In one mode, the charging system inhibits overcharging of the batteries. In a further variation, the charging system seeks to maintain the voltages of the batteries within a predetermined charge range (i.e., between an undercharged value and a fully charged value).

Abstract: An outboard motor comprises an engine mounted within an engine compartment. The engine comprises an induction system having an induction passage extending between an air intake box to a combustion chamber. A throttle valve is positioned along the passage. A bypass passage communicates with the passage at a location between the throttle valve and the combustion chamber. An adjustable valve controls flow through the bypass passage. The adjustable valve is opened as the throttle valve is opened or as the engine speed is increased. The adjustable valve is closed when the throttle valve is rapidly closed or when the engine speed is rapidly decreased.

Abstract: An engine for a marine vehicle includes a controller having a predetermined map defining a relationship between a fuel injection parameter and an engine operation characteristic. Additionally, the controller includes at least one compensation factor for adjusting the fuel injection parameter. The compensation value is derived from data recorded during a test of the engine. The compensation factor is used during the normal operation of the engine to achieve a predetermined air/fuel ratio.

Abstract: A fuel injection system for a marine engine includes an improved construction that, by the introduction of lubricant into the fuel, inhibits components of the system from rusting in the event that water, particularly salt water, is mixed with the fuel. The engine includes a lubricant delivery system to deliver lubricant to at least one portion of the engine that needs lubrication. A premix lubricant pump is provided for supplying lubricant with the fuel injection device from the lubricant delivery system so as to mix the part of the lubricant to the fuel. An ECU controls an amount of the part of the lubricant so as to be in a proper and extremely small range.

Abstract: A four-cycle engine includes an improved construction that is provided with an air induction system, which is suitable for low speed engine operations and which can provide an easy assembling and/or maintenance work. The engine has multiple cylinders arranged in a V-configuration. An air induction system supplies air to combustion chambers of the cylinders and includes a pair of plenum chamber members. The plenum chamber members are generally disposed on an opposite side of a crankcase relative to a crankshaft. Both the plenum chamber members are positioned in close vicinity to each other. Each one of the plenum chamber members defines a plenum. A balance pipe is affixed to both the plenum chamber members to couple together the plenum chambers.

Abstract: An induction system for a watercraft includes a first intake air chamber communicating with at least one combustion chamber of an engine of the watercraft, and a second intake air chamber communicating with the first intake air chamber via a conduit. The second intake air chamber may be arranged in various orientations and/or with various other features which improve attenuation of induction noises and/or the preclusion of water from entering the engine through the induction system.

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: An engine for an outboard motor includes engine components disposed around the engine body. A cooling system includes a first water passage cooling the engine body and a second water passage branching off from the first water passage upstream the engine body and extending through the engine components. One engine component is generally positioned above the engine body. Two engine components are positioned on different sides of the engine body. The first and second water passages have separate discharge ports. The engine components are made of a metal material. The second water passage is defined by tubular members made of a corrosion-resistant material and the respective tubular members are embedded in the respective bodies of the engine components.

Abstract: An exhaust system for an outboard motor includes an improved construction that can be compact enough for the limited space afforded within a powerhead of an outboard motor. The outboard motor includes an engine and a support member arranged to support the engine. The engine includes a cylinder block that defines a plurality of cylinder bores. The cylinder bores extend generally horizontally and spaced apart vertically from each other to form a cylinder bank extending generally vertically. At least two exhaust manifolds extend generally vertically aside and along the cylinder bank. Pistons reciprocate within the cylinder bores. A cylinder head closes ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons. The cylinder head further defines at least one exhaust port per each one of the combustion chambers. Exhaust passages communicate with the exhaust ports.

Abstract: A starting fuel supplying apparatus improves restarting performance of an engine in a warm-up state. In the engine in which a carburetor is disposed on the side of the cylinder, the starting fuel supplying apparatus and a thermo-sensitive member attached to the carburetor are disposed on the side of the carburetor close to the engine.

Abstract: A fuel injection system for an engine includes an improved construction and provides a method for releasing a needle valve which has adhered to a valve seat in a fuel injector. The fuel injector is a normally closed type and the valve is activated by a solenoid to part from the valve seat to inject fuel. A first power supply unit is provided to supply electric power to the solenoid under an ordinary operating condition of the engine. A second power supply unit is additionally provided to supply electric power greater than the power supplied by the first power supply unit. In one embodiment, the second power supply unit includes a booster to raise the voltage. A switchover mechanism, such as detachable couplers, are provided to switch over between the first power supply unit and the second power supply unit.

Abstract: A watercraft has an engine that is controlled to reduce the likelihood of engine stall when the watercraft engine speed is rapidly decreased while the watercraft is in a planing mode. The engine is controlled by a method that detects a rapid engine speed decrease when the watercraft is believed to be in the planing mode. A operational characteristic of the engine is adjusted to increase the engine speed such that, after the engine reaches a stable engine speed, the stable engine speed is higher than a desired idle speed. The operational characteristic can be an advance in ignition timing or an increase in airflow to the engine.

Abstract: An exhaust system for a watercraft includes an improved construction of an exhaust silencer in which inlet and outlet conduits are arranged without interfering with each other. An inlet conduit is arranged to deliver the exhaust gases to the silencer. An outlet conduit is arranged to discharge the exhaust gases from the silencer. The silencer includes a main body defining a first chamber. The inlet conduit is coupled with the main body to communicate with the first chamber. The silencer further includes a side body bulging laterally outward from the main body. The side body defines a second chamber communicating with the first chamber. The outlet conduit is coupled with the side body to communicate with the second chamber.

Abstract: An engine includes an air induction system, a fuel supply system, a lubrication system and a ventilation system. The fuel supply system has a fuel reservoir in which a space for fuel vapors is defined. The lubrication system lubricates a component of the engine with lubricant. The ventilation system couples a crankcase of the engine with the air induction system so as to deliver oil vapors in the crankcase to the air induction system. A fuel vapor passage is arranged to couple the space of the fuel reservoir with the ventilation system.

Abstract: A lubricant filter mounting structure for a internal combustion engine includes a lubricant filter mounting surface and a catch member. The lubricant filter mounting surface is positioned at an angle with respect to a vertical plane, and the catch member is mounted at least partially directly below a lubricant filter. At least a portion of the induction system and at least a portion of the exhaust system is removeably mounted to the engine to enhance access to the filter, especially within the confined engine compartment of a personal watercraft.

Abstract: A power head for an outboard motor includes an improved construction that can includes a compactly arranged tilt relay unit of a hydraulic tilt and trim system. The outboard motor includes a drive unit comprising an internal combustion engine. A bracket assembly is adapted to be mounted on an associated watercraft. The bracket supports the drive unit for pivotal movement about a generally horizontally extending tilt axis. A hydraulic tilt system is arranged to tilt up and down the drive unit. The tilt system includes a hydraulic pump and an electric motor actuating the hydraulic pump. A tilt relay unit supplies electric power to the electric motor based upon a control signal. The relay unit is disposed generally between the engine and the bracket assembly.