Abstract: A marine muffler includes a housing having a wet exhaust inlet, a water outlet, and a dry exhaust outlet. An internal chamber is divided by an angularly disposed baffle into lower and upper chambers. Vertical exhaust ducts penetrate the baffle and function to allow exhaust gas and entrained cooling water to pass from the lower chamber into the upper chamber. The second chamber is bounded at the top a second baffle which terminates the upward flow of exhaust thereby redirecting the exhaust downward. A pair of exhaust conduits extend through the second baffle thereby allowing exhaust to pass upward and into a third chamber which is bounded at it's uppermost portion by a third baffle defining a plurality of slotted apertures in fluid communication with the exhaust outlet. Water separated from the exhaust gas is directed to the water outlet by the diagonal baffle whereby it exits the housing.

Abstract: A marine muffler includes a housing having a wet exhaust inlet, a water outlet, and a dry exhaust outlet. An internal chamber is divided by an angularly disposed baffle into lower and upper chambers. Vertical exhaust ducts penetrate the baffle and function to allow exhaust gas and entrained cooling water to pass from the lower chamber into the upper chamber. The second chamber is bounded at the top a second baffle which terminates the upward flow of exhaust thereby redirecting the exhaust downward. A pair of exhaust conduits extend through the second baffle thereby allowing exhaust to pass upward and into a third chamber which is bounded at it's uppermost portion by a third baffle defining a plurality of slotted apertures in fluid communication with the exhaust outlet. Water separated from the exhaust gas is directed to the water outlet by the diagonal baffle whereby it exits the housing.

Abstract: A marine muffler capable of handling both marine engine exhaust gas and marine engine cooling water includes a double wall baffle partitioning the muffler interior so as to function as a cooling water conduit. The cooling water conduit includes an inlet disposed external to the main muffler housing and an outlet configured and disposed so as to discharge the engine cooling water into the exhaust duct connected to the muffler outlet. The muffler is thus able to convey the engine cooling water through the muffler housing within a dedicated conduit while maintaining the cooling water separate from the exhaust gas. A muffler that is adapted to handle both the exhaust and cooling water flowing from a marine engine allows for the elimination of engine cooling water piping.

Abstract: A stern drive is for propelling a marine vessel in water. The stern drive is configured to power a propulsor located below the surface of the water. The stern drive comprises an internal combustion engine that powers a driveshaft that axially extends through a transom of the marine vessel; an exhaust manifold that conveys exhaust gas from the internal combustion engine; and an elongated exhaust conduit that redirects the exhaust gas from the exhaust manifold transversely with respect to the driveshaft. The elongated exhaust conduit conveys the exhaust gas to an upstream exhaust outlet that discharges the exhaust gas through the transom below the surface of the water and then to a downstream exhaust outlet that is spaced apart from and is located vertically higher than the upstream exhaust outlet. The elongated exhaust conduit functions as a water lift muffler during operation of the stern drive.

Abstract: The present invention refers to a suction chamber having two volume parts which utilizes the principle of wave cancellation, by reversing the phase thereof, as a way of attenuating the noise, whose configuration presents a simple, effective, economical and affordable constructive process.

Abstract: To reduce or eliminate the startle response in aquatic life, embodiments of the present invention alter the sound produced by a diver's exhaled bubbles by adjusting up or down the frequency of the sound produced by the bubbles.

Abstract: An ear tip piece device made of resilient material dimensioned for fitting the ear canal of a user, having a solid portion, a reversibly compressible portion and a first channel. In one embodiment, the ear tip piece is asymmetrical due to a bend. In another alternative embodiment, the ear tip piece has a second channel that is used for allowing natural transmission of sound to the ear.

Abstract: Air bubbles may be used to reduce radiated underwater noise. Two modalities of sound attenuation by air bubbles were shown to provide a reduction in radiated sound: bubble acoustic resonance damping and acoustic impedance mismatching. The bubbles used for acoustic resonance damping were manifested using gas-filled containers coupled to a support, and the acoustic impedance mismatching bubbles were created using a cloud of freely-rising bubbles, which were both used to surround an underwater sound source.

Abstract: To reduce or eliminate the startle response in aquatic life, embodiments of the present invention alter the sound produced by a diver's exhaled bubbles by adjusting up or down the frequency of the sound produced by the bubbles.

Abstract: Air bubbles may be used to reduce radiated underwater noise. Two modalities of sound attenuation by air bubbles were shown to provide a reduction in radiated sound: bubble acoustic resonance damping and acoustic impedance mismatching. The bubbles used for acoustic resonance damping were manifested using gas-filled containers coupled to a support, and the acoustic impedance mismatching bubbles were created using a cloud of freely-rising bubbles, which were both used to surround an underwater sound source.

Abstract: Disclosed are apparatus and methodology for reducing noise and wear in a flapper configured exhaust tip for a marine exhaust system. A metallic flapper is located at an end portion of an exhaust tip of the exhaust pipe. An elastomeric flapper assembly is provided covering the exhaust tip and includes a lip portion configured to provide noise reduction by functioning as a stop for a tip portion of the metallic flapper. The metallic flapper is positioned such that a tip thereof contacts the elastomeric flapper assembly rather than the metallic exhaust pipe. Such contact with an elastomeric flapper assembly reduces noise previously produced by flapper contact with the hot exhaust pipe.

Abstract: A marine muffler comprises an elongate cylindrical housing having an inlet and an outlet and defining an internal volume partitioned, by an angularly disposed internal baffle, into a lower chamber in communication with the inlet and an upper chamber in communication with the outlet. A vertically disposed duct is insertably secured to the baffle to allow exhaust gas and exhaust cooling water to flow from the lower inlet chamber to upper outlet chamber. The exhaust duct may preferably be further adapted with internal structure forming a plurality of individual flow conduits or passages. The duct is preferably positioned such that a plurality of flow passage inlets are positioned in proximity to the lower cylindrical housing wall, with flow passage outlets positioned in proximity to the upper housing wall. The lower duct wall may further be adapted with sidewall apertures for improving exhaust flow dynamics therethrough.

Abstract: To reduce or eliminate the startle response in aquatic life, embodiments of the present invention alter the sound produced by a diver's exhaled bubbles by adjusting up or down the frequency of the sound produced by the bubbles.

Abstract: Disclosed are apparatus and methodology for reducing noise and wear in a flapper configured exhaust tip for a marine exhaust system. A flapper, normally located within an exhaust tip of a marine exhaust system, is relocated upstream of the point in the exhaust system where cooling water normally contacts the exhaust pipe. An exhaust tip is coupled to the upstream portion of the exhaust system by way of an elastomeric coupling device. The flapper is positioned such that a tip thereof contacts the elastomeric coupling rather than the metallic exhaust pipe. Such contact with an elastomeric coupling device reduces noise previously produced by flapper contact with the hot exhaust pipe occasioned by destruction and/or heat degeneration of elastomeric material generally associated with the flapper device.

Abstract: An exhaust apparatus for a small boat for reducing exhaust noise. A water muffler is provided at a midsection of the exhaust pipes extending from an engine which is provided in a boat body. An interior of the water muffler is partitioned into an expansion chamber and a resonator chamber with a front exhaust pipe connected to the engine and a rear exhaust pipe opening out of the boat being interlinked with the expansion chamber. The resonator chamber is directly connected to the midsection of the rear exhaust pipe via a connecting pipe. The water muffler is arranged in a longitudinal direction that is oriented in the fore-and-aft direction so as to extend along the side of a pump chamber in which a jet pump driven by the engine is arranged. A second resonator chamber is arranged along the water muffler on the outer side of the water muffler.

Abstract: Disclosed are apparatus and methodology for reducing noise and wear in a flapper configured exhaust tip for a marine exhaust system. A metallic flapper is located at an end portion of an exhaust tip of the exhaust pipe. An elastomeric flapper assembly is provided covering the exhaust tip and includes a lip portion configured to provide noise reduction by functioning as a stop for a tip portion of the metallic flapper. The metallic flapper is positioned such that a tip thereof contacts the elastomeric flapper assembly rather than the metallic exhaust pipe. Such contact with an elastomeric flapper assembly reduces noise previously produced by flapper contact with the hot exhaust pipe.

Abstract: Disclosed are apparatus and methodology for reducing noise and wear in a flapper configured exhaust tip for a marine exhaust system. A flapper, normally located within an exhaust tip of a marine exhaust system, is relocated upstream of the point in the exhaust system where cooling water normally contacts the exhaust pipe. An exhaust tip is coupled to the upstream portion of the exhaust system by way of an elastomeric coupling device. The flapper is positioned such that a tip thereof contacts the elastomeric coupling rather than the metallic exhaust pipe. Such contact with an elastomeric coupling device reduces noise previously produced by flapper contact with the hot exhaust pipe occasioned by destruction and/or heat degeneration of elastomeric material generally associated with the flapper device.

Abstract: To reduce or eliminate the startle response in aquatic life, embodiments of the present invention alter the sound produced by a diver's exhaled bubbles by adjusting up or down the frequency of the sound produced by the bubbles.

Abstract: An exhaust apparatus for a small boat for reducing exhaust noise. A water muffler is provided at a midsection of the exhaust pipes extending from an engine which is provided in a boat body. An interior of the water muffler is partitioned into an expansion chamber and a resonator chamber with a front exhaust pipe connected to the engine and a rear exhaust pipe opening out of the boat being interlinked with the expansion chamber. The resonator chamber is directly connected to the midsection of the rear exhaust pipe via a connecting pipe. The water muffler is arranged in a longitudinal direction that is oriented in the fore-and-aft direction so as to extend along the side of a pump chamber in which a jet pump driven by the engine is arranged. A second resonator chamber is arranged along the water muffler on the outer side of the water muffler.

Abstract: To provide an exhaust structure for a small watercraft that can cool exhaust gas, reduce the size and weight, and thereby cost of a backflow prevention chamber. An exhaust structure for a small watercraft is configured to be able to cool exhaust gas in the course of leading it to the outside when the exhaust gas of an engine is led to the outside for discharge. This exhaust structure includes a water muffler containing water therein. A backflow prevention chamber is disposed above the water muffler and adapted to prevent water from entering the side of the engine from the side of the water muffler. The backflow prevention chamber is provided with a cooling water injecting portion adapted to spray cooling water to the exhaust gas in an internal space. An outlet is formed in the bottom portion of the backflow prevention chamber to communicate with the water muffler.

Abstract: A system for reducing the infrar d visibility of an amphibious vehicle that generates hot exhaust gas when it is in a body of water has a nozzle directed downward at and closely juxtaposed with a surface of the body of water. This nozzle expels the hot exhaust gas downward at the surface so as to form a water-droplet cloud that cools the gas and masks the vehicle. the nozzle is set at an angle of at most 60° to vertical.

Abstract: A marine engine muffler is provided having a silencing element with an inclined surface defining an array of elongate slotted apertures generally disposed in circumferential alignment. The slotted apertures are preferably defined by angled sidewalls such that exhaust gas flowing therethrough is forced to travel in a path that forms a reverse angle relative to the overall exhaust flow path thus conducting exhaust gases and entrained water to reverse direction while flowing through the silencing element. The conical silencing element is specifically sized to avoid resonant vibration within the operational RPM range of the engine and is further sized relative to the combined displacement of the engine and/or cylinder bank in fluid communication therewith to avoid resonant vibrations caused by reflected exhaust gas pressure waves generated by the internal combustion engine.

Abstract: A muffler is provided for a marine propulsion system in which an initial portion causes a downward flow of exhaust gas and entrained water from an exhaust manifold. The transition section directs the exhaust gas toward an egress section which extends upwardly from the transition section. The various sections of the exhaust path can be configured to form one or more loops which define one or more water collection regions.

Abstract: A silencer is disclosed that reduces the acoustic energy of a fluid mixture of a liquid coolant and of exhaust gas from an engine. The engine may be a marine engine. The silencer according to this aspect includes a receiving chamber that receives the fluid mixture and exhaust gas, at least one lifting conduit; and a separation chamber. The lifting conduit has a receiving portion with a first opening and an expelling portion with a second opening. The receiving portion is fluidly coupled with the receiving chamber so that the fluid mixture enters the first opening from the receiving chamber and is lifted through the lifting conduit to the expelling portion. This lifting may be accomplished, at least in part, by dynamic effects. The separation chamber is fluidly coupled with the second opening of the lifting conduit, and has at least one interior surface.

Abstract: A marine engine muffler is provided having a silencing element with an inclined surface defining an array of elongate slotted apertures generally disposed in circumferential alignment. The slotted apertures are preferably defined by angled sidewalls such that exhaust gas flowing therethrough is forced to travel in a path that forms a reverse angle relative to the overall exhaust flow path thus conducting exhaust gases and entrained water to reverse direction while flowing through the silencing element. The conical silencing element is specifically sized to avoid resonant vibration within the operational RPM range of the engine and is further sized relative to the combined displacement of the engine and/or cylinder bank in fluid communication therewith to avoid resonant vibrations caused by reflected exhaust gas pressure waves generated by the internal combustion engine.

Abstract: A wet marine exhaust muffler includes a metallic housing and a polymeric jacket substantially encapsulating the metallic housing. The metallic housing defines one or more chambers in the interior of the housing. An inlet pipe and an outlet pipe each extend through openings in the polymeric jacket and communicate with at least one chamber in the interior of the housing. The metallic housing is preferably formed from stainless steel and the polymeric jacket is preferably formed from a thermoplastic material having a thickness of approximately 0.001 inch to 0.1 inch, and more preferably of approximately 0.005 inch to 0.060 inch.

Abstract: A silencer is provided for a marine diesel engine. The silencer comprises a conical silencer element (20) located within an exhaust duct (10), the silencer element having apertured surfaces which are inclined to the flow of exhaust gases in the duct.

Abstract: A muffler for muffling the exhaust sound of a motor boat having a diesel motor. The exhaust gases of the motor are led to a buffer chamber that is located beneath the waterline of the boat and mounted on a trim tab fitted to the transom of the boat. The bottom of the chamber is formed by the trim tab and includes a slot, which extends transversely to the direction of water flow. A flow casing through which exhaust gases exit into the water is provided beneath the slot.

Abstract: An improved muffler for silencing the exhaust emitted from a water cooled marine engine employing a first outer housing encompassing a generally cone shaped inner member and forming a silencing volume therebetween and an angularly disposed inner planar baffle, inlet path, outlet path, ramp, and aperture for exhaust gas and cooling water to fluidly communicate from an inlet to an outlet resulting in a diminution in flow velocity so as to attenuate the exhaust noise.

Abstract: An improved muffler for silencing the exhaust emitted from a marine engine employing a reverse entry inlet conduit, an attenuation chamber and an outlet conduit whereby exhaust gas and liquid is communicated through the inlet conduit and into the attenuation chamber against the direction of the outlet stream. Upon entering the attenuation chamber exhaust gases and liquids reflect off the inner walls of the chamber and incoming exhaust thereby attenuating exhaust noise until they are finally forced out of the attenuation chamber through the outlet conduit. The reverse entry design of the muffler provides protection against backwardly flowing water that commonly enters a marine exhaust system by orienting the direction of inlet flow at an angle which is greater than 0 degrees but less than 90 degrees relative to the direction of output flow from the muffler.

Abstract: An exhaust muffler for small marine craft that can be located in the rear portion of the bilge and straddle the drive shaft and the shaft log. The muffler has a shell formed from sides, ends, top and bottom walls. The bottom wall is provided with a concave depression to receive the shaft and shaft log. A preferred configuration of the depression is a semi-conical surface having a base proximate the inlet wall. Further, the top and bottom walls are configured to conform to the undersurface of the deck and the inside of the hull, respectively. An inlet pipe, or a multiple number of inlet pipes, receive exhaust gases and water from the exhaust manifold of the craft engine and direct this combination into the muffler above a water pool. Gases pass through the water pool and exit through an outlet pipe (or a plurality of outlet pipes). A downwardly extending conduit within the outlet pipe(s) provides a correct amount of lift such that an amount of water exits the muffler which is the same as the amount entering.

Abstract: A wet marine exhaust muffler comprises a housing, an inlet pipe and an outlet pipe. The housing includes end walls each transverse with respect to an imaginary plane and converging side walls connecting converging edges of the end walls such that the converging side walls are symmetrical with respect to the imaginary plane. The inlet pipe extends through a first of the end walls, while the outlet pipe extends through a second of the end walls. Preferably, the converging side walls of the housing are so dimensioned as to conform to a converging lower hull portion of a boat to minimize the space occupied by the wet marine exhaust muffler. In an especially preferred form of the invention, at least one of the pipes in the wet marine exhaust muffler includes a notched upstream end portion and a cap positioned against the upstream end portion to define a radial opening to impart a swirling type vector to the flow as it enters the pipe.

Abstract: A muffler is described for use in connection with an exhaust passage in a ongated shaft rotating about a longitudinal axis. The shaft exhausts exhaust material generated by an internal or external combustion engine, having both a gaseous and a liquid material. The muffler includes a series of partitions situated transverse to the longitudinal axis of the shaft, each partition defining a central aperture to facilitate passage of gaseous material from an input end of the exhaust shaft to an output end of the exhaust shaft, and at least one exterior aperture proximate the sidewall of the exhaust passage to facilitate passage of liquid material from the input end to the output end. The central and exterior passages tend to separate the gaseous and liquid material in the exhaust. The series of partitions define chambers which attenuates the sound energy in the exhaust.

Abstract: An exhaust silencing system for a small planing craft includes a first expansion chamber housing on one side of a water craft which transmits exhaust gases and waste cooling water to a second expansion chamber housing which may have a number of expansion chambers. A long exhaust pipe extends from the second expansion chamber housing to the atmosphere.

Abstract: An improved muffler for silencing the exhaust emitted from a water cooled marine engine comprising a housing enclosure having a corrugated spacing means disposed within the housing partitioned by an angularly disposed inner planar baffle, the housing having an inlet for the exhaust gas and cooling water to fluidly communicate with a lower silencing chamber wherein the exhaust gas and cooling water are forced through a spacer passageway formed from the corrugated spacing means into an upper silencing chamber resulting in flow reversal and diminution in flow velocity so as to attenuate the exhaust noise, the exhaust gas and cooling water exiting the upper silencing chamber through an outlet fluidly communicated therewith and disposed collinearly with the input. The upper silencing chamber acting as a back flow preventor.

Abstract: An improved muffler for silencing the exhaust emitted from a water cooled marine engine employing a first housing encompassing a second housing which is partitioned by an angularly disposed inner planar baffle further having an inlet for exhaust gas and cooling water to fluidly communicate into an inlet chamber of the second housing resulting in a diminution in flow velocity so as to attenuate the exhaust noise, the exhaust gas and cooling water exiting the inlet chamber through an aperture fluidly communicated therewith into a silencing volume formed by an area between the first and second housing and forced through an aperture into an outlet chamber of said second housing. The outlet chamber acting as a back flow preventor.

Abstract: An exhaust muffler for outboard motors which is fastened to the rear end of the propeller hub and directs the motor's exhaust back into the hub of the propeller and out through the front of the propeller and the by-pass exhaust ports of the motor. The muffler includes an elastomeric member and a blocking member with the blocking member having pressure relief mechanism therein.

Abstract: An outboard motor comprising a propulsion unit including a propeller shaft, and an internal combustion engine drivingly connected to the propeller shaft and including a V-shaped cylinder block having first and second cylinder banks including respective first and second cylinders having respective first and second exhaust ports, and the cylinder block defining an exhaust chamber communicating with the exhaust ports, a cowling surrounding the engine and including an upper portion and a lower portion, a muffler located between the cylinder banks and including an inner cover portion which has therein an exhaust inlet communicating with the exhaust chamber and which engages the cylinder block, an outer cover portion, and a main cover portion which is located between the inner and outer cover portions and which defines an exhaust outlet and an expansion chamber communicating between the exhaust inlet and the exhaust outlet, and an exhaust conduit extending through the lower cowling portion and communicating between

Abstract: An exhaust muffler for mounting on the transom of a powerboat in association with the exhaust pipes which extend through the transom. The muffler comprises a housing extending laterally across the stern of the boat and rearwardly from the transom to define an interior space. The housing has a floor located below the water line; opposed end walls; a front wall located adjacent to the transom with openings formed therein, through which exhaust gas can pass from the exhaust pipes; a rear wall having exhaust ports formed therein and a cover that encloses the interior space. Located within the enclosed space are muffler inserts secured to the floor and also to the front and rear walls. Each insert has a domed portion defining a muffling chamber that communicates with the respective exhaust pipe, and a second domed chamber defining an expansion chamber that communicates with the respective exhaust port located in the rear wall of the housing.

Abstract: A muffler is provided for sound dampening of wet exhaust gases. The muffler comprises a canister, or housing, having an inlet and an outlet. The housing is preferably constructed of a plurality of resealable interlocking sections which can be disengaged from one another to allow opening and closing of the housing to permit exposure of the sound dampening element(s) for inspection and replacement thereof or to allow for removal, servicing and replacement of the sound dampening element(s) which are positioned therein. The sound dampening element(s) can be formed from a foamed, heat resistant moldable material, such as a closed-cell concrete.

Abstract: A muffler for an exhaust system of an outboard engine is constructed in two parts, one being longer than the other with the longer portion being of standard length for various engine applications, while the shorter length muffler section is constructed to have variable lengths to accommodate various engine and propulsion unit applications. The lower muffler section is resiliently mounted to reduce transmittal of vibrations to the engine housing and associated structure. By constructing one of the muffler sections of a standard length for all engine applications, molding costs for various applications are reduced.

Abstract: An improved muffler for silencing the exhaust emitted from a water cooled marine engine employing a first housing encompassing a second housing which is partitioned by an angularly disposed inner planar baffle further having an inlet for exhaust gas and cooling water to fluidly communicate into an inlet chamber of the second housing resulting in a diminution in flow velocity so as to attenuate the exhaust noise, the exhaust gas and cooling water exiting the inlet chamber through an aperture fluidly communicated therewith into a silencing volume formed by an area between the first and second housing and forced through an aperture into an outlet chamber of said second housing. The outlet chamber acting as a back flow preventor.

Abstract: A muffler for use with an underwater vehicle. The muffler is mechanically attached to an exhaust tube or aft end of the underwater vehicle and has an hydrodynamic shape and perforated exterior that results in the production of less noise by the vehicle. Large bubbles have been determined to be offensive due to lower frequency collapsing noise which produces a louder vehicle exhaust. The present invention is perforated with holes to break up the flow of exhaust gas from the vehicle into small diameter bubbles that are emitted into the water. The present invention has a contoured outer wall that matches the contour of the underwater vehicle to provide for the hydrodynamic flow of water around the vehicle as it is propelled through the water. The present invention eliminates hydrodynamic voids at the aft end of the vehicle that would normally allow smaller bubbles to coalesce into large bubbles.

Abstract: An improved muffler for silencing the exhaust emitted from a water cooled marine engine comprising a housing enclosure partitioned by an angularly disposed inner planar baffle, the housing having an inlet for the exhaust gas and cooling water to fluidly communicate with a lower silencing chamber wherein the exhaust gas and cooling water are forced through a central passageway into an upper silencing chamber resulting in flow reversal and diminution in flow velocity so as to attenuate the exhaust noise, the exhaust gas and cooling water exiting the upper silencing chamber through an outlet fluidly communicated therewith and disposed collinearly with the input. The upper silencing chamber acting as a back flow preventor.

Abstract: The invention provides a marine propulsion device comprising a powerhead including an exhaust gas discharge port, a gearcase rotatably supporting a propeller shaft connected to the powerhead and including an exhaust gas discharge, and a lower unit including an upper portion supporting the powerhead and a lower portion connected to the gearcase, with the lower unit comprising an inner exhaust housing having a generally vertical wall, an open top in communication with the powerhead exhaust gas discharge port, a bottom having therein a first exhaust gas outlet and a second exhaust gas outlet at the top portion of the wall, and an outer exhaust housing also having a generally vertical wall in surrounding relation to the inner exhaust gas housing and defining a vertically extending generally annular space between the inner and outer exhaust gas housings, the space communicating with the second exhaust gas outlet.

Abstract: A number of embodiments of internal combustion engine exhaust systems each of which is effective to provide good silencing for exhaust gases through the use of an elastic diaphragm that dampens pulsations. In some embodiments, this elastic diaphragm forms a portion of a Helmholz resonator and in some the diaphragm is cooled by submerging in a cooling jacket of the engine or its exhaust system or by means of cooling air fins. Also, various arrangements are incorporated for adjusting or tuning the rigidity of the diaphragm. Furthermore, in some embodiment the diaphragm is suspended in such a way as to act as a vibration damping member between mechanical components of the exhaust system.

Abstract: Sound muffling devices for marine engines for installation on the external portion of the transom of a marine vessel are attached in such a manner that any breakdown within the silencer causes no discharge of exhaust gases or cooling fluids into the interior of the vessel and the gases and cooling fluid continue to be discharged overboard. The silencers are designed to reduce, substantially, the noise level emitted by the engine under operation by the efficient mixture of gases and water through a series of baffles, with low resistance to gas flow that does not diminish engine efficiency. At high speeds the gases and odors are emitted from the vessel at the centerline with distance and direction such as to reduce, substantially, emissions into the air environment. The device receives exhaust gas and cooling water from an exhaust pipe passing through the transom at the side of the boat and directs the gas athwart the boat to the center where it is exhausted.

Abstract: Sound muffling devices for marine engines for installation on the external portion of the transom of a marine vessel are attached in such a manner that any breakdown within the silencer causes no discharge of exhaust gases or cooling fluids into the interior of the vessel and the gases and cooling fluid continue to be discharged overboard. The silencer is designed to reduce, substantially, the noise level emitted by the engine under operation by the efficient mixture of gases and water through a series of baffles, with low resistance to gas flow that does not diminish engine efficiency. The gases and odors are emitted from the vessel at the centerline with distance and direction such as to reduce, substantially, emissions into the air environment. The device receives exhaust gas and cooling water from an exhaust pipe passing through the transom at the side of the boat and directs the gas athwart the boat to the center where it is exhausted.

Abstract: A number of embodiments of silencing devices for marine propulsion units using acoustical lenses that are positioned across either the air inlet device, the air exhaust device or both. The acoustical lenses direct the sound waves in such a way so as to effect silencing while, at the same time, ensuring that water will not enter the engine combustion chambers. The invention is shown in conjunction with both outboard motors and inboard mounted engines.

Abstract: Disclosed herein is an inner exhaust gas housing adapted to be located within a drive shaft housing of an outboard motor, which inner exhaust gas housing integrally includes an open upper end, a first exhaust passage extending downwardly from the upper end, a second exhaust passage extending downwardly from the upper end, an expression chamber adjacent the upper end, a first passage communicating between the first and second exhaust passages and the expansion chamber, and a second passage communicating with the expansion chamber and with the atmosphere exterior to the inner exhaust gas housing.