Abstract: A sound attenuation system for a compressor of a direct fuel injected engine of an outboard motor comprises a discharge sound attenuator connected in fluid communication with an air distribution manifold outlet and a suction sound attenuator connected in fluid communication with the suction port of a compressor. In a typical application of the present invention, the air distribution manifold is connected in fluid communication with a discharge port of the compressor. Both the discharge sound attenuator and the suction sound attenuator can further include filter media disposed within their internal cavities.

Abstract: A water reservoir is provided for use in conjunction with the engine of a marine propulsion system. The water reservoir is shaped to comprise two or more water containment cavities that can be located in positions which absorb heat from various heat producing components of the engine and, in addition, serve as sound barriers to attenuate noise emanating from the engine. The water reservoir is connected in fluid communication with the water pump of the marine propulsion system and in fluid communication with a cooling system of the engine.

Abstract: An oil reservoir is used as a sound attenuator in an outboard motor and is placed under the cowl of the outboard motor with the throats of the engine's throttle bodies disposed between the oil reservoir and the engine itself. This allows the sound emanating from the throttle bodies to be attenuated by the oil reservoir which is cup-shaped to partially surround the throat of the throttle bodies. A plate member can be attached to a hollow wall structure in order to enclose a cavity therebetween. The structure therefore serves as an oil reservoir for the engine and also as a sound attenuating member.

Abstract: An exhaust system for an outboard motor (10) includes a main exhaust passageway (16) extending through a partially water filled chamber (17) in the drive shaft housing (13). An inlet idle relief passage (23) connects the top of the chamber (17) with the main exhaust passageway (16) and an outlet passage (24) connects the top of the chamber (17) with the atmosphere. The system thus defines an effective exhaust silencer for the idle exhaust.