Patent Publication Number: US-11655784-B1

Title: Marine engine assembly having an air pump

Description:
CROSS-REFERENCE 
     The present application claims priority to U.S. Provisional Application No. 62/968,855, filed Jan. 31, 2021, the entirety of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present technology relates to marine engine assemblies and more specifically water intrusion prevention in internal combustion engines of marine engine assemblies. 
     BACKGROUND 
     A typical marine outboard engine assembly is formed from an engine unit with an internal combustion engine, a lower unit with a propeller, and a midsection connecting the engine to the propeller. The midsection also has an exhaust channel to bring exhaust from the engine to be expelled out through the lower unit. 
     The outboard engine assembly is generally connected to its corresponding watercraft by a transom or mounting bracket, typically connected to the midsection, below the engine unit. The bracket connects to a rear portion of the watercraft, such that the engine unit and part of the midsection is well above the water. In some cases, however, it could be preferable to have a marine engine which is disposed lower relative to the watercraft to allow more useable room in the watercraft for example. 
     However, by positioning the marine engine lower, a portion of the engine unit, and therefore the engine, will likely be below the water level at least some of the time, risking water intrusion in the engine. When the engine is operating, the flow of exhaust gases out of the marine engine is usually sufficient to prevent water intrusion into the engine via the exhaust system. However, when the engine is stopped, the flow of exhaust gases stops, and the risk of water entering the exhaust system, and potentially the engine under some circumstances, is greater. 
     Therefore, there is a desire for a marine engine assembly having features assisting in the prevention of water intrusion in the engine. 
     SUMMARY 
     It is an object of the present technology to ameliorate at least some of the inconveniences present in the prior art. 
     According to one aspect of the present technology, there is provided a marine engine assembly for mounting to a watercraft. The marine engine assembly has an engine unit including: an engine unit housing; an internal combustion engine disposed in the engine unit housing, the engine defining at least one combustion chamber; and an air intake assembly disposed in the engine unit housing, the air intake assembly defining an air inlet, the air intake assembly being fluidly connected to the at least one combustion chamber for supplying air to the at least one combustion chamber, the air intake assembly including a throttle valve. The marine engine assembly also includes an exhaust system fluidly communicating with the at least one combustion chamber for supplying exhaust gases from the at least one combustion chamber to an exterior of the marine engine assembly. The exhaust system defines an exhaust outlet. The air intake assembly, the at least one combustion chamber, and the exhaust system together defining at least in part a gas flow pathway. The air inlet defines an upstream end of the gas flow pathway. The exhaust outlet defines a downstream end of the gas flow pathway. The marine engine assembly also includes a sealing valve provided in the gas flow pathway between the air inlet and the exhaust outlet. The sealing valve has an open position permitting flow of gas therethrough. The sealing valve has a closed position preventing flow of gas therethrough for sealing a portion of the gas flow pathway downstream of the sealing valve from a portion of the gas flow pathway upstream of the sealing valve. The marine engine assembly also has an air pump being configured for supplying air to the gas flow pathway downstream of the sealing valve; and a propulsion device operatively connected to the engine. 
     In some embodiments, the air pump is disposed inside the engine unit housing; and the air pump is configured for supplying air from inside the engine unit housing to the gas flow pathway. 
     In some embodiments, in the closed position, the sealing valve hermetically seals the portion of the gas flow pathway downstream of the sealing valve from the portion of the gas flow pathway upstream of the sealing valve. 
     In some embodiments, the sealing valve is disposed upstream of the engine. 
     In some embodiments, the sealing valve is disposed downstream of the throttle valve. 
     In some embodiments, the air pump supplies air to the gas flow pathway at a position upstream of the engine. 
     In some embodiments, the air intake assembly includes an intake manifold fluidly connected to the engine; and the air pump supplies air in the air intake manifold. 
     In some embodiments, the air pump supplies air in the air intake system. 
     In some embodiments, the exhaust system includes an idle relief passage. The idle relief passage has an idle relief passage inlet communicating with the gas flow pathway at a position upstream of the exhaust outlet and an idle relief passage outlet at a position vertically higher than the exhaust outlet at least when the marine engine assembly is in a trim range. The air pump supplies air to the gas flow pathway at a position upstream of the idle relief passage inlet. 
     In some embodiments, a sealing valve actuator is operatively connected to the sealing valve for moving the sealing valve between the open position and the closed position. An engine management module (EMM) disposed in the engine unit housing and being in communication with the sealing valve actuator and the air pump. The EMM controls the sealing valve actuator such that the sealing valve is in the open position when the engine is in operation. The EMM controls the sealing valve actuator such that the sealing valve is in the closed position when the engine is stopped. The EMM controls the air pump to supply air to the gas flow pathway in response to at least one predetermined condition. 
     In some embodiments, an exhaust water level sensor is disposed in the exhaust system and communicates with the EMM. The at least one predetermined condition includes the EMM receiving a signal from the exhaust water level sensor indicating that water in the exhaust system has reached a level of the water level sensor. 
     In some embodiments, the at least one predetermined condition includes the sealing valve being closed. 
     In some embodiments, a lower unit is connected to the engine unit. The lower unit includes: a lower unit housing fastened to the engine unit housing; a transmission disposed in the lower unit housing, the transmission being operatively connected to the engine; and the propulsion device being operatively connected to the transmission. 
     In some embodiments, the propulsion device is a propeller; and the exhaust outlet is defined in the propeller. 
     In some embodiments, the engine unit housing defines an aperture fluidly communicating an interior of the engine unit housing with air exterior to the engine unit housing. 
     In some embodiments, an external conduit is fluidly connected to the aperture and is disposed externally of the engine unit housing. At least one line extends from a component disposed inside the engine unit housing. The at least one line extends inside the external conduit. The at least one line is at least one of a power line, a communication line and a fuel line. 
     In some embodiments, a transom bracket is connected to the engine unit housing. The transom bracket defines a tilt-trim axis. A center of mass of the engine is disposed below the tilt-trim axis at least when the marine engine assembly is in a trim range. 
     According to another object of the present technology, there is provided a method for preventing intrusion of water into a combustion chamber of an internal combustion engine of a marine engine assembly from an exhaust system of the marine engine assembly. The method comprising: determining, by an engine management module (EMM), that water in the exhaust system has reached a predetermined level; and in response to determining that water in the exhaust system has reached the predetermined level, the EMM controlling an air pump to supply air to a gas flow pathway of the marine engine assembly. The gas flow pathway is defined at least in part by an air intake assembly of the marine engine assembly, the combustion chamber, and the exhaust system. An air inlet of the air intake assembly defines an upstream end of the gas flow pathway. An exhaust outlet of the exhaust system defining a downstream end of the gas flow pathway. 
     In some embodiments, determining, by the EMM, that water in the exhaust system has reached the predetermined level comprises receiving a signal from an exhaust water level sensor disposed in the exhaust system at the predetermined level, the signal from the exhaust water level sensor being indicative that water in the exhaust system has reached the predetermined level. 
     In some embodiments, the method further comprises the EMM controlling the air pump to stop supplying air in response to the EMM receiving a signal from the exhaust water level sensor that water in the exhaust system is below the predetermined level. 
     In some embodiments, in response to determining that water in the exhaust system has reached the predetermined level, the EMM controls the air pump to supply air to the air intake assembly. 
     In some embodiments, the method further comprises determining, by the EMM, that the engine has stopped; and in response to determining that the engine has stopped, the EMM controls a sealing valve actuator to close a sealing valve. The sealing valve is disposed in the gas flow pathway. When closed, the sealing valve prevents flow of gas therethrough by sealing a portion of the gas flow pathway downstream of the sealing valve from a portion of the gas flow pathway upstream of the sealing valve. In response to determining that water in the exhaust system has reached the predetermined level, the EMM controls the air pump to supply air to the gas flow pathway downstream of the sealing valve after the sealing valve is closed. 
     In some embodiments, the sealing valve is disposed upstream of the engine. 
     In some embodiments, the sealing valve is disposed downstream of the throttle valve. 
     In some embodiments, in response to determining that water in the exhaust system has reached the predetermined level, the EMM controls the air pump to supply air to the gas flow pathway downstream of the sealing valve and upstream of the engine. 
     For purposes of this application, terms related to spatial orientation such as forward, rearward, upward, downward, left, and right, should be understood in a frame of reference of the marine engine assembly, as it would be mounted to a watercraft with a marine engine in a neutral trim position. Terms related to spatial orientation when describing or referring to components or sub-assemblies of the engine assembly separately therefrom should be understood as they would be understood when these components or sub-assemblies are mounted in the marine engine assembly, unless specified otherwise in this application. The terms “upstream” and “downstream” should be understood with respect to the normal flow direction of fluid inside a component. As such, in an engine assembly, the air intake system is upstream of the engine and the exhaust system is downstream of the engine. Similarly, for a component having an inlet and an outlet, the inlet is upstream of the outlet, and the outlet is downstream of the inlet. The term “hermetically sealed” should be understood to mean that the passage of gas through the associated device is prevented, such as in an airtight manner. 
     Explanations and/or definitions of terms provided in the present application take precedence over explanations and/or definitions of these terms that may be found in any documents incorporated herein by reference. 
     Embodiments of the present technology each have at least one of the above-mentioned object and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein. 
     Additional and/or alternative features, aspects and advantages of embodiments of the present technology will become apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where: 
         FIG.  1    is a right side elevation view of a watercraft having a marine engine assembly according to the present technology; 
         FIG.  2    is a right side elevation view of the marine engine assembly of the watercraft of  FIG.  1   ; 
         FIG.  3    is a right side elevation view of the marine engine assembly of  FIG.  2   , with a portion of a housing of the marine engine assembly having been removed; 
         FIG.  4    is a left side elevation view of the marine engine assembly of  FIG.  3   ; 
         FIG.  5    is a top plan view of the marine engine assembly of  FIG.  3   ; 
         FIG.  6    is a rear elevation view of the marine engine assembly of  FIG.  3   ; 
         FIG.  7    is a perspective view, taken from a rear, right side of a vertical cross-section of an engine, an exhaust system and other components of the marine engine assembly of  FIG.  3   , the vertical cross-section being taken laterally through a center of a middle cylinder of the engine; 
         FIG.  8    is a perspective view, taken from a rear, right side of a vertical cross-section of the marine engine assembly of  FIG.  3   , taken through line  8 - 8  of  FIG.  3   ; 
         FIG.  9    is a vertical cross-section view of a front portion of the marine engine assembly of  FIG.  3   , with the engine and some associated components having been remove, the vertical cross-section being taken longitudinally along a lateral center of the marine engine assembly; 
         FIG.  10    is a perspective view taken from a front, right side of an air intake valve unit and an air intake plenum of the marine engine assembly of  FIG.  3   ; 
         FIG.  11    is a perspective view, taken from a front, right side of a vertical cross-section of the air intake valve unit and the air intake plenum of  FIG.  10   , the cross-section being taken longitudinally; 
         FIG.  12    is a vertical and longitudinal cross-section taken along a lateral center of the air intake valve unit and the air intake plenum of  FIG.  10   , with a throttle valve and a sealing valve of the air intake valve unit both being closed; 
         FIG.  13    is the cross-section of  FIG.  12   , with the throttle valve and the sealing valve both being open; 
         FIG.  14    is a perspective view taken from a rear, right side of an alternative embodiment of the air intake valve unit of  FIG.  10   ; 
         FIG.  15    is a bottom view of the air intake valve unit of  FIG.  14   ; 
         FIG.  16    is a cross-sectional view of the air intake valve unit of  FIG.  14   , taken through line  16 - 16  of  FIG.  15   , with a throttle valve of the air intake valve unit being closed and a sealing valve of the air intake valve unit being open; 
         FIG.  17    is an outlet end view of the air intake valve unit of  FIG.  14   , with the throttle valve being closed and the sealing valve being open; 
         FIG.  18    is the cross-sectional view of  FIG.  16   , the throttle valve and the sealing valve both being closed; 
         FIG.  19    is an outlet end view of the air intake valve unit of  FIG.  14   , with the throttle valve and the sealing valve both being closed; 
         FIG.  20    is a schematic representation of some components of the marine engine assembly of  FIG.  2    involved in an operation of the sealing valve of the air intake valve unit of  FIG.  14    and in an operation of an air pump of the marine engine assembly of  FIG.  2   ; 
         FIG.  21    is a flowchart illustrating the operation of the sealing valve of the air intake valve unit of  FIG.  14   ; and 
         FIG.  22    is a flowchart illustrating the operation of the air pump of  FIG.  20   . 
     
    
    
     It should be noted that the Figures are not necessarily drawn to scale. 
     DETAILED DESCRIPTION 
     The present technology is described with reference to its use in a marine engine assembly  100  that is used to propel a watercraft and is configured to be disposed under the deck of the watercraft it propels. It is contemplated that aspects of the present technology could be used in other types of marine engine assemblies, such as in a marine outboard engines having an engine unit, a midsection connected below the engine unit, a lower unit connected below the midsection, and a transom bracket configured to connect the midsection to a watercraft. 
     In  FIG.  1   , a watercraft  10  is illustrated. The watercraft  10  is specifically a pontoon boat  10 , but this is simply one non-limiting example of a watercraft according to the present technology. This particular embodiment of the boat  10  includes a watercraft body  12  formed generally from two pontoons  14  (only one being illustrated) and a platform  16 . 
     The boat  10  also includes a marine engine assembly  100 , also referred to herein as the assembly  100 . The assembly  100  is pivotably and rotatably connected to the watercraft body  12  for providing propulsion via a propulsion device  102 . The propulsion device  102  is specifically a propeller  102  in the present embodiment, but it is contemplated that the propulsion device  102  could be different in some embodiments. 
     The assembly  100  includes a transom bracket  104  which is fastened to the watercraft body  12 . As is shown schematically, the transom bracket  104  is connected to a lower portion of the platform  16 , such that the assembly  100  is generally disposed below a top surface  18 , also called the deck  18 , of the platform  16  laterally between the pontoons  14 . 
     With additional reference to  FIGS.  2  to  6   , the marine engine assembly  100 , shown separately from the watercraft  10 , will now be described in more detail. The assembly  100  includes an engine unit  106 , a lower unit  108 , and the transom bracket  104 . 
     The engine unit  106  includes an engine unit housing  110  for supporting and covering components disposed therein. The housing  110  is sealed such that water in which the engine unit housing  110  is immersed is impeded from entering the engine unit housing  110  during normal operating conditions, including when at rest, and components of the engine inside the housing  110  are water-proofed to the same degree as in a conventional outboard engine. Depending on the specific embodiment of the housing  110  and methods used to produce a generally water-tight seal, the housing  110  could be water-proof to varying degrees. It is contemplated that the housing  110  could receive different treatments to seal the housing  110  depending on the specific application for which the marine engine assembly  100  is going to be used. In the present embodiment, the housing  110  includes a cowling  112 . The cowling  112  is fastened to the rest of the housing  110  along a diagonally extending parting line  114 . A seal (not shown) is provided between the cowling  112  and the rest of the housing  110  along the parting line. 
     The engine unit  106  includes an internal combustion engine  116  disposed in the engine unit housing  110  for powering the assembly  100  and for driving the propeller  102 . By removing the cowling  112 , the engine  116  can be accessed, as shown in  FIGS.  3  to  6   . In the present embodiment, the internal combustion engine  116  is a three-cylinder, two-stroke, gasoline-powered, direct injected internal combustion engine. It is contemplated that the internal combustion engine  116  could be a four-stroke internal combustion engine. It is contemplated that the engine  116  could have more or less than three cylinders. In some embodiments, the internal combustion engine  116  could use a fuel other than gasoline, such as diesel. 
     With reference to  FIG.  7   , the engine  116  includes a crankcase  118 . A cylinder block  120  defining three cylinders  122  (one of which is shown) is disposed above the crankcase  118 . A cylinder head  124  is disposed on top of the cylinder block  120 . Each cylinder  122  has a piston  126  reciprocally received inside of it. Each piston  126  is connected by a corresponding connecting rod  128  to a crankshaft  130 . The crankshaft  130  rotates in the crankcase  118 . For each cylinder  122 , the piston  126 , the cylinder  122  and the cylinder head  124  define together a combustion chamber  132 . For each combustion chamber  132 , a direct fuel injector  134  supported by the cylinder head  124  is provided to inject fuel into the combustion chamber  132 , and a spark plug  136  extends into the combustion chamber  132  through the cylinder head  124  to ignite an air-fuel mixture inside the combustion chamber  132 . 
     The engine  116  includes one air intake  138  per cylinder  122 . The air intakes  138  are provided at the bottom of the crankcase  118 . Air is delivered to the air intakes  138  by an air intake assembly  140  ( FIG.  3   ), described in more detail below, as indicated by arrow  142 . The air passes through reed valves  144  provided in the crankcase  118  adjacent the air intakes  138 . The reed valves  144  allow air to enter the crankcase  118  but help prevent air from exiting the crankcase  118 . For each cylinder  122 , a transfer port  146  communicates the crankcase  118  with the corresponding combustion chamber  132  for air to be supplied to the combustion chamber  132  as indicated by arrow  148 . 
     Each combustion chamber  132  has a corresponding exhaust port  150 . Exhaust gases flow from the combustion chambers  132 , through the exhaust ports  150 , into an exhaust manifold  152  as indicated by arrow  154 . Each exhaust port  150  has a corresponding reciprocating exhaust valve  155  that varies the effective cross-sectional area and timing of its exhaust port  150 . From the exhaust manifold  152 , the exhaust gases are routed out of the marine engine assembly  100  via the other portions of an exhaust system  156  (some of which are shown in  FIGS.  8  and  9   ), described in more detail below. 
     The reciprocation of the pistons  126  causes the crankshaft  130  to rotate. The crankshaft  130  drives an output shaft  158  ( FIGS.  8  and  9   ) which drives the propeller  102 , as is described in more detail below. With reference to  FIG.  2   , a center of mass  160  of the engine  116  is disposed vertically in a lower half of the engine unit  110 , and longitudinally about halfway along a length of the crankshaft  130 , although the exact position of the center of mass  160  depends on the details of a particular embodiment of the engine  116 . 
     Returning to  FIGS.  2  to  5   , the transom bracket  104  includes a watercraft portion  162  which is adapted for fastening to the watercraft body  12 . The bracket  104  also includes an engine portion  164 , pivotally connected to the watercraft portion  162 , and which is fastened to the engine unit housing  110 . The engine portion  164  is pivotable with respect to the watercraft portion  162  about a tilt-trim axis  166 . The transom bracket  104  thus defines the tilt-trim axis  166  of the marine engine assembly  100 , about which the assembly  100  can be trimmed or tilted relative to the watercraft body  12 . The engine portion  164  of the transom bracket  106  includes a tilt/trim actuator  168  (not shown in  FIGS.  2  to  5   , schematically shown in  FIG.  20   ) for tilting or trimming the assembly  100  relative to watercraft body  12 . In one embodiment, the tilt/trim actuator  168  is a linear hydraulic actuator adapted for pushing the engine portion  164  away from the watercraft portion  162 , but other types of tilt/trim actuators  168  are contemplated, such as that described in US Patent Application Publication No. 2019-0233073, the entirety of which is incorporated herein by reference. The engine portion  164  includes steering actuator  170  configured for steering the engine unit  106  and the lower unit  108  relative to the transom bracket  104  about a steering axis  172  ( FIG.  5   ). In the present embodiment, the steering actuator  170  is a rotary hydraulic actuator, but other types of steering actuators  170  are contemplated. 
     As can be seen in  FIG.  2   , the center of gravity  160  of the engine  116  is disposed below the tilt-trim axis  116 , when the assembly  100  is in a trim range. As the assembly  100  is designed to be disposed below the deck  18 , the engine  116  and the transom bracket  104  partially vertically overlap, rather than the engine  116  being disposed well above the bracket  104  as would be the case in a conventional outboard engine assembly meant to extend higher relative to the watercraft body  12 . In the present embodiment, the center of gravity  160  is vertically between a top end of the transom bracket  104  and a bottom end of the transom bracket  104 . 
     Turning now to  FIG.  9   , the lower unit  108  includes a lower unit housing  174 , which is fastened to the engine unit housing  110 . The lower unit  108  also includes a driveshaft  176 , a transmission  178 , a propeller shaft  180  and the propeller  102 . The driveshaft  176  is driven by the output shaft  158  via bevel gears  182 . The driveshaft  176  drives the transmission  178 . The transmission  178  selectively drives the propeller shaft  180  to which the propeller  102  is connected. The assembly  100  is said to be in the trim range when the propeller shaft  180  is less than fifteen degrees from horizontal. In other embodiments, this angle could be different, such as thirty degrees from horizontal for example. 
     The lower unit housing  174  defines an exhaust passage  184  for receiving exhaust from the engine  116 . The exhaust passage  184  is fluidly connected with channels  186  near the propeller shaft  180 . The channels  186  fluidly connect to passages  188  in the propeller  102  which allow exhaust gas to leave the marine engine assembly  100  under water. 
     With additional reference to  FIGS.  2 ,  3 ,  6 ,  10  and  11   , the air intake assembly  140  will now be described in more detail. As mentioned above, the air intake assembly  140  is disposed in the engine unit housing  110 . The air intake assembly  140  forms a conduit between an exterior of the engine unit housing  110  and the engine  116  for providing air for combustion. The air intake assembly  116  is sealed such that surrounding fluids in the engine unit housing  110 , such as any air and water present in the engine unit housing  110 , are impeded from entering the air intake assembly  140  and thereby will not enter the engine  116  via the air intake assembly  140 . Instead, the air intake assembly  140  delivers air from outside the housing  110  to the engine  116  directly, delivering the air needed for combustion in the engine  116 . 
     As best seen in  FIG.  6   , the air intake assembly  140  extends generally along the right side of the engine unit housing  110  and is disposed mainly between the engine  116  and the right side of the housing  110  and partially below the engine  116 . In some embodiments, all or part of the air intake assembly  140  could extend along the left, front, rear, top or other sides of the housing  110 , depending on the arrangement of the engine  116  and more specifically the arrangement of the engine air intakes  138 . It is also contemplated that all or part of the air intake assembly  140  could extend above the engine  116 , depending on the particular embodiment of the engine  116 . 
     The air intake assembly  140  defines an air inlet  190  in the engine unit housing  110  on a top, front, right side thereof, that fluidly communicates with air exterior to the engine unit housing  110  and three outlets (not shown) fluidly connected to the three air intakes  138  of the engine  116 . The air inlet  190  is fluidly connected to an external conduit  192  ( FIG.  2   ). The external conduit  192  includes an inlet  194  ( FIG.  2   ) located onboard the watercraft  10 . The external conduit  192  is supported by the watercraft body  12 . The external conduit  192  delivers air from above the water line to the air intake assembly  140 , via the external conduit  192 . 
     Additional components of the air intake assembly  140  will now be described in more detail. An intake conduit  196  ( FIG.  5   ) connects to the air inlet  190  and extends rearward and downward therefrom inside the engine unit housing  110  on a right side of the engine  116 . An air intake valve unit  200  disposed on a right side of the engine  116  has an upstream end connected to a downstream end of the intake conduit  196 . The air intake valve unit  200  has valve  204  that acts as both a throttle valve and a sealing valve ( FIG.  11   ). The air intake valve unit  200  will be described in more detail below. A plenum  206  is connected to a downstream end of the air intake valve unit  200 . As can be seen in  FIG.  3   , the plenum  206  diverges as it extends rearward and downward from the air intake valve unit  200 . As can be seen in  FIG.  6   , the lower end of the plenum  206  is connected to an air intake manifold  208 . The air intake manifold  208  connects to the bottom of the crankcase  118  to supply air to the air intakes  138  of the engine  116 . It is contemplated that some or all of the components of the air intake assembly  140  could be disposed on any other side or sides of the engine  116 . 
     As can be seen in  FIG.  3   , an air pump  210  is disposed inside the engine unit housing  110 . The air pump  210  is powered by a battery (not shown) provided on the boat  10 . The air pump  210  is connected to a right side of the engine  116  below the air intake unit  200  and in front of the plenum  206 . It is contemplated that the air pump  210  could be provided elsewhere inside the engine unit housing  110 . The air pump  210  selectively supplies air from inside the engine unit housing  110  to the air intake manifold  208  as will be described in more detail below. 
     As can be seen in  FIG.  5   , the engine unit housing  110  defines an aperture  212  on a top, front, left side thereof, that fluidly communicates with air exterior to the engine unit housing  110 . The aperture  212  is fluidly connected to an external conduit  214  ( FIG.  4   ). The external conduit  214  includes an inlet  216 . The external conduit  214  is supported by the watercraft body  12 . The external conduit  214  is used for the routing of lines  218  that extend from components disposed inside the engine unit housing  110 , then pass through the aperture  212  and the external conduit  214  to connect to components provided on the watercraft  10 . The lines  218  include, but are not limited to, battery cables to connect components inside the engine unit housing  110  to one or more batteries provided on the watercraft  10 , communication lines for exchanging signals between components inside the engine unit housing  110  and components provided on the watercraft  10  such as display gauges, a throttle input, and a transmission input, and a fuel line for supplying fuel from a fuel tank on the watercraft  10  to the fuel injectors  134 . It is also contemplated that the lines  218  can include an oil supply hose for connecting an oil pump inside the engine unit housing  110  with an external oil tank located onboard the watercraft  10 . The external conduit  214  also allows the exchange of air between an exterior of the engine unit housing  110  above the water line and the inside of the engine unit housing  110 , thereby permitting the air pump  210  to supply this air to the air intake assembly  140 . 
     Turning now to  FIGS.  7  to  9   , the exhaust system  156  will be described in more detail. As previously mentioned and as shown in  FIG.  7   , each combustion chamber  132  has a corresponding exhaust port  150 . Exhaust gases flow from the combustion chambers  132 , through the exhaust ports  150 , into the exhaust manifold  152  as indicated by arrow  154 . From the exhaust manifold  152 , the exhaust gases flow forward into an exhaust pipe (not shown) and then into an exhaust pipe  220  located at a front of the engine unit housing  110 , in front of the engine  116 . As can be seen in  FIG.  8   , the exhaust pipe  220  extends upward, then curves and extends downward, thus forming a gooseneck having an apex  222 . Exhaust gas flows in the exhaust pipe  220  in the direction indicated by arrow  224 . The inner portion  226  of the apex  222  is vertically higher than the top of the combustion chambers  132  when the marine engine assembly  100  is in the trim range to help prevent intrusion of water into the combustion chambers  132  from the exhaust system  156 . From the exhaust pipe  220 , the exhaust gas flows downward and under the output shaft  158  via an exhaust passage  228 , as indicated by arrow  230 . From the exhaust pipe  228 , the exhaust gases enter the lower unit housing  174 . With reference to  FIG.  9   , as indicated by arrow  232 , the exhaust gases flow through the exhaust passage  184 , then through the channels  186 , and finally through the passages  188  in the propeller  102 . The ends of the passages  188  define the exhaust gas outlets  234  of the exhaust system  156 . 
     During operation of the marine engine assembly  100 , such as when the engine is idling or operating at trolling speeds, the exhaust gas pressure may become too low to keep the water out of the lower portion of the exhaust system  156 . Under these conditions, this can result in water entering the passages  188 , the channels  186 , the exhaust passage  184 , and rising into the exhaust passage  228  up to the same level as the water outside of the marine engine assembly  100  (i.e. up to the waterline). As this water blocks the exhaust outlets  234 , the exhaust system  156  includes an idle relief passage  236  to allow the exhaust gases to flow out of the marine engine assembly  100  to the atmosphere. With reference to  FIG.  8   , the idle relief passage  236  has an idle relief passage inlet  238  communicating with the exhaust passage  228 . As indicated by the dotted-line arrow  240 , from the idle relief passage inlet  238  the exhaust gases flow left trough a passage  242 , then through a tortuous passage  244 . With reference to  FIGS.  4  to  6   , from a top of the tortuous passage  244 , the exhaust gases flow rearward through an idle relief muffler  246  disposed on top of the engine  116  as indicated by dotted-line arrow  248 . From the idle relief muffler  246 , the exhaust gases flow through a pipe  250  that extends through a rear of the cowling  112 . The outlet of the pipe  250  is an idle relief passage outlet  252  of the idle relief passage  236 . The idle relief passage outlet  252  is near a top of the engine unit housing  110  so as to be above the waterline during typical operation of the marine engine assembly  100 . It is contemplated that the idle relief passage outlet  252  could be disposed on the front, top or sides of the engine unit housing  100 . It is contemplated that the idle relief passage outlet  252  could be located at other positions that are vertically higher than the exhaust outlets  234  at least when the marine engine assembly  100  is in the trim range. It is contemplated that the idle relief muffler  246  could be omitted. 
     The air intake assembly  140 , the crankcase  128 , the transfer ports  146 , the combustion chambers  132 , and the exhaust system  156  together define a gas flow pathway. The gas flow pathway is the path through which gas (air or exhaust gas depending on the location) flows from the point it enters the engine unit housing  110  to be supplied to the engine  116  to the point at which it is exhausted from the marine engine assembly  100 . The air inlet  190  defines the upstream end of the gas flow pathway. The exhaust outlets  234  define the downstream end of the gas flow pathway. In embodiments where the engine  116  is a four-stroke engine, as the engine  116  has no transfer ports, and since the air does not flow through the crankcase before reaching the combustion chambers, the gas flow pathway would not include the crankcase and transfer ports. 
     As described above, the marine outboard engine  100  is provided with various features to help prevent entry of water into the combustion chambers  132  of the engine  116 . Although these are effective for most conditions, there could be some rare conditions, especially when the engine  116  is stopped, where additional protection against water intrusion may be useful. Examples of such possible conditions could include a lot of weight being on the boat  10  above the marine engine assembly  100  causing it to sink into water much lower than it typically does, the boat  10  and marine engine assembly  100  being launched in the water at a steep angle and/or at higher than normal speed, and rough water conditions. 
     To provide additional protection against water intrusion into the combustion chamber  136  from the exhaust system  156 , the marine engine assembly  100  is provided with the valve  204 , which acts as a sealing valve  204 . When the sealing valve  204  is open, gas can flow through the gas flow pathway. However, when the sealing valve  204  is closed, flow of gas through the sealing valve  204  is prevented, and the sealing valve  204  thus hermetically seals the portion of the gas flow pathway downstream of the sealing valve  204  from the portion of the gas flow pathway upstream of the sealing valve  204 . As a result, when the sealing valve  204  is closed, should water rise into the exhaust system  156  rise above the idle relief passage inlet  238 , the gas present between the sealing valve  204  and the water having entered the exhaust system  156  is trapped and has nowhere to go. As such, this volume of air acts like an air spring pushing against the water, thus resisting increases in water level in the exhaust system  156 . In embodiments where no idle relief passage  236  is provided the entire volume of gas between the sealing valve  204  and the exhaust outlets  234  could act like an air spring resisting increases in water level in the exhaust system  156 . 
     In the present embodiment, the sealing valve  204  is provided in the air intake valve unit  200  and also combines the function of a throttle valve. It is contemplated that in other embodiments, two separate valves could be provided, one throttle valve and one sealing valve, and that the sealing valve could be in any location along the gas flow pathway. It is contemplated that the sealing valve  204  could be provided in the gas flow pathway at positions upstream of the combustion chambers  132 , or upstream of the engine  116 . It is contemplated that the sealing valve  204  could be provided in the gas flow pathway at positions downstream the engine  116 . 
     Turning now to  FIGS.  10  to  13   , the intake valve unit  200  will be described in more detail. The intake valve unit  200  has a valve unit body  260 . The valve unit body  260  has an upstream end  262  and a downstream end  264 . The sealing valve  204  includes a cap  266 , a streamlined body  268 , a spring  270 , a seal  272 , and a shaft  276  pivotally supporting a cam  278  in the valve unit body  260 . The cap  266  is disposed in the valve unit body  260  between the shaft  276  and the downstream end  264 . The cap  266  translates between an open position, shown in  FIGS.  11  and  13   , and a closed position, shown in  FIG.  12   , as will be described below to define the open and closed positions of the sealing/throttle valve respectively. The streamlined body  268  is fixedly mounted in the valve unit body  260  downstream of the cap  266 . As can be seen, the spring  270  is mounted inside the streamlined body  268  and abuts an inner surface of the cap  266 . The spring  270  biases the cap  266  toward the closed position. In the closed position, the cap  266  is spaced from the streamlined body  268  and abuts the seal  272  provided in the valve unit body  260 , thereby preventing flow of gas through the sealing valve  204  for hermetically sealing the portion of the valve unit body  260  downstream of the cap  266  from the portion of the valve unit body  260  upstream of the cap  266 . In the open position, air can flow through the sealing/throttle valve  204 . More specifically, the cap  266  is pushed against the front end of the streamlined body  268 , such that the cap  266  and the streamlined body  268  form a generally teardrop shaped body so as to limit the turbulence created by the presence of the cap  266  and the streamlined body  268  in the air flowing through the valve unit body  260 . 
     The intake valve unit  200  also has an actuator  274  disposed outside of the valve unit body  260 . In the present embodiment, the actuator  274  is an electric motor, but other types of actuators are contemplated. The actuator  274  is connected to the shaft  276  for pivoting the cam  278 . The cam  278  abuts the upstream side of the cap  266 . To move the sealing/throttle valve  204  its open position ( FIG.  13   ), the cam  278  pushes the cap  266  toward the streamlined body  268 , and as a result the sealing/throttle valve  204  opens. To move the sealing/throttle valve  204  to its closed position ( FIG.  12   ), the cam  278  is moved to the position shown in  FIG.  1    such that it no longer pushes against the cap  266  and the spring  270  pushes the cap  266  against the seal  272 . As a result the sealing/throttle valve  204  is closed. By pivoting the cam  278 , position of the cap  266  is controlled, which controls the amount of air flowing through the intake valve unit  200 , and as such the valve  204  acts as a throttle valve. Also, since the cap  266  provides a hermetic seal when it is pushed against the seal  272 , the valve  203  also acts as a sealing valve. 
     Turning now to  FIGS.  14  to  19   , an intake valve unit  300 , which is an alternative embodiment of the intake valve unit  200 , will be described. The intake valve unit  300  has a valve unit body  302 . The valve unit body  302  has an upstream end  304  and a downstream end  306 . 
     A throttle valve  308  is pivotally disposed in the valve unit body  302 . A throttle valve actuator  310  disposed outside of the valve unit body  302 . In the present embodiment, the throttle valve actuator  310  is an electric motor, but other types of actuators are contemplated. The throttle valve actuator  310  is connected to a shaft  312  pivotally supporting the throttle valve  308  in the valve unit body  302  for moving the throttle valve  308  between opened and closed positions. 
     A sealing valve  314  is disposed in the valve unit body  302  between the throttle valve  308  and the downstream end  306 . In the present embodiment, the sealing valve  314  is a ball valve  314 . The ball valve  314  has a ball valve body  316  defining a passage  318  therethrough. The ball valve body  316  is pivotally received in a seat  319  define by the valve unit body  302 . The ball valve body  316  is operatively connected to a sealing valve actuator  320  disposed outside of the valve unit body  302 . In the present embodiment, the sealing valve actuator  320  is an electric motor, but other types of actuators are contemplated. The sealing valve actuator  320  pivots the ball valve body  316  between open and closed positions corresponding to open and closed positions of the ball valve  314 . 
     In the open position of the ball valve  314 , shown in  FIGS.  16  and  17   , the passage  318  of the ball valve body  316  is aligned with the passage  322  defined by the valve unit body  302 , and gas can flow through the ball valve  314 . In the closed position of the ball valve  314 , shown in  FIGS.  18  and  19   , the ball valve body  316  is pivoted such that outer surfaces  324  of the ball valve body  316  block the passage  322 , thereby preventing flow of gas through the ball valve  314  for hermetically sealing the portion of the valve unit body  302  downstream of the ball valve  314  from the portion of the valve unit body  302  upstream of the ball valve  314 . It is contemplated that a sealing valve of a type other a ball valve could be used. For example, it is contemplated that a guillotine valve or a butterfly valve could be used as the sealing valve  314 . As the intake valve unit  300  has different actuators  310  and  320  used for moving the throttle valve  308  and the sealing valve  314 , the sealing valve  314  can be move independently of the throttle valve  308  and vice versa. 
     Turning now to  FIG.  20   , components of the marine engine assembly  100  (but provided with the intake valve unit  300  instead of the intake valve unit  200 ) involved in an operation of the sealing valve  314  of the air intake valve unit  300  and in an operation of the air pump  210  will be described. 
     An engine management module (EMM)  350  is provided inside the engine unit housing  110 . The EMM  350  includes multiple processors and data storage modules. The EMM  350  is connected to and controls the operation of the engine  116 , including the starter motor  352 , the tilt/trim actuator  168 , the air pump  210  and the sealing valve actuator  320 . In order to control these components, the EMM  350  is connected to and receives signals from an exhaust water level sensor  354 , an exhaust pressure sensor  356 , a temperature sensor  358 , an engine speed/crankshaft position sensor  360 , a sealing valve position sensor  362  as well as other sensors provided on the engine  116 , in the marine engine assembly  100 , such as a throttle valve position sensor (not shown), and on the boat  10 , such as a shift lever position sensor (not shown). 
     As can be seen in  FIG.  8   , the exhaust water level sensor  354  is located in the exhaust pipe  220 , at a position downstream of the apex  222  and upstream of the idle relief passage inlet  238 . When water makes contact with the exhaust water level sensor  354 , the sensor  354  sends a signal to the EMM  350  indicating that water has reached this level in the exhaust system  156  and that some actions should be taken as will be described below. As can also be seen in  FIG.  8   , the exhaust pressure sensor  356  is also located in the exhaust pipe  220 , at a position downstream of the apex  222  and upstream of the idle relief passage inlet  238 . It is contemplated that the exhaust pressure sensor  356  could be at other locations in the exhaust system  156  upstream of the idle relief passage inlet  238 , or that the exhaust pressure sensor  356  could be omitted. The exhaust pressure sensor  356  sends a signal indicative of gas pressure in the exhaust system  156 . The temperature sensor  358  could be an exhaust temperature sensor sensing temperature in the exhaust system  156 , an intake air temperature sensor sensing temperature in the air intake assembly  140 , or a temperature sensor sensing temperature in the engine unit housing  110  around the engine  116 . It is contemplated that one or more of these temperature sensors could be provided to send signals indicative of temperature to the EMM  350 . For simplicity, the present will refer only to one temperature sensor  358 , that could be any one or combinations of the aforementioned temperature sensors. 
     The engine speed/crankshaft position sensor  360  is located close to the crankshaft  130  or to an element that turns at the same speed as the crankshaft (such as a flywheel for example) to send signals to the EMM  350  that let the EMM  350  determine the orientation of the crankshaft  130 , which allows the EMM  350  to know where each of the pistons  126  are positioned, and the speed of rotation of the crankshaft  130 . When the engine  116  is first engaged by the starter  354  in order to start then engine  116 , the EMM  350  is able to determine the position of the crankshaft  130  within the first or the first few rotations of the crankshaft  130  using the signals from the engine speed/crankshaft position sensor  360 . This process of initially determining the position of the crankshaft  130  by the EMM  350  is sometimes referred to as synchronizing of the EMM  350  or “synch”. If the EMM  350  is unable to synch, the starter motor  352  will be de-energized and the engine  116  will not be started. 
     The sealing valve position sensor  362 , as its name suggest, sends a signal to the EMM  350  indicative of the position of the sealing valve  314 . It is contemplated that the sealing valve position sensor  362  could be integrated with the sealing valve actuator  320  or could be a dedicated sensor sensing the position of sealing valve  314 . It is also contemplated that the sealing valve position sensor  362  could only provide an indication of whether the sealing valve  314  is open or closed, without an exact indication of its position. 
     Turning now to  FIG.  21   , a method  400  of operating the sealing valve  314  will be described. The method  400  begins at step  402  when the EMM  350  is awakened or turned on. In a boat  10  requiring a key to permit starting of the engine  116 , this corresponds to when the key is inserted and at least partially turned, hence the name “key on” of step  402  in  FIG.  21   . It is contemplated that in boats  10  that does not require a key, this could correspond to the actuation of a button, a switch, a combination of buttons, or the detection of proximity of a remote fob or of the press of a button on the remote fob. 
     When the engine  116  stops running, the EMM  350  sends a signal to the sealing valve actuator  320  to close the sealing valve  314 , as will be explain below with respect to step  426 . Accordingly, from step  402 , at step  404  the EMM  350  determines if the sealing valve  314  is closed (as it should be). If not, at step  406  the EMM  350  records a fault, does not allow cranking (i.e. starting) of the engine  116 , and sends signals to provide an indication of this to the driver of the boat  10 . The indication could be visual, such as a light turning on a console, or auditory, such as one or more beeps. 
     If at step  404 , the sealing valve  314  is closed, then at step  408  the EMM  350  determines if the exhaust water level sensor  354  is okay, meaning that it does not detect the presence of water. If water is detected, then the EMM  350  goes to step  406  described above. If the exhaust water level sensor  354  does not detect the presence of water, then at step  410  the EMM  350  checks if a start command has been issued. This could be the above mentioned key being turned to a start position, or a start button being pressed for example. The EMM  350  will hold at step  410  until a start command is issued. 
     Once a start command is issued, then at step  412  the EMM  350  sends a signal to the starter motor  352  to engage the engine  116  and start turning the crankshaft  130 . Then at step  414 , the EMM  350  determines if the above-mentioned synchronization (synch) of the EMM  350  has been achieved. If not, then the EMM  350  sends a signal to the starter  352  to de-energize at step  416  and then returns to step  404 . If synchronization is achieved, at step  418  the EMM  350  sends a signal to the sealing valve actuator  320  to open the sealing valve  314 . It is contemplated that in an alternative embodiment, the EMM  350  could send a signal to the sealing valve actuator  320  to at least partially open the sealing valve  314  slightly prior to or at the same time as performing step  412 , then if synchronization is not achieved at step  414 , the EMM  350  would send a signal to the sealing valve actuator  320  to close the sealing valve  314  before returning to step  404 . 
     Once the sealing valve  314  is open, then at step  420  the EMM  350  determines if the engine  116  is running. This can be done by determining if the engine speed is higher than a predetermined speed for example, which would indicate that the engine  116  can turn the crankshaft  130  without the assistance of the starter  352 . If the engine  116  is not running after a predetermined period of time, the EMM  350  sends a signal to the sealing valve actuator  320  to close the sealing valve  314  at step  422 , then goes to step  416  where the starter  352  is de-energized as indicated above, and the returns to step  404 . 
     If at step  420  it is determined that the engine  116  is started, the EMM  350  sends a signal to de-energize the starter motor  350  (not shown), and then the EMM  350  monitors if the engine  116  is running at step  424 . The EMM  350  will hold at step  424  as long as the engine  116  is running. Once the engine  116  stops running, then at step  426  the EMM  350  sends a signal to the sealing valve actuator  320  to close the sealing valve  314 , thus helping to prevent the intrusion of water into the combustion chambers  132  via the exhaust system  156  while the engine  116  is stopped, as described above. Then at step  428 , the EMM  350  determines if the key has been removed (hence the name “key off”) or an equivalent action that results in the EMM  350  being put to sleep, such as pressing an off button for example. If not, then the EMM  350  returns to step  404 . If so, then the EMM  350  moves to step  502  of method  500  described below. 
     It is contemplated that a time delay could be applied before closing the sealing valve  314  at step  426 . The reason for doing so would be to take into account thermal contraction of the gas into the gas flow pathway. When the engine  116  stops, the air in the gas flow pathway is hot. As it cools, the air contract which could reduce the volume of air trapped by the sealing valve  314  if the sealing valve  314  is closed right away. As such waiting for the gas in the gas flow path to cool before closing the sealing valve  314  could help prevent the reduction of gas volume due to thermal contraction. The time could be a set amount of time or an amount of time based on the temperature sensed by the temperature sensor  358 . It is also contemplated that when the engine  116  stops running and the sealing valve  314  is closed, the EMM  350  could send a signal to the tilt/trim actuator  168  to trim the marine engine assembly  100  up, thus lifting the marine engine assembly  100  partially out of water. 
     If at any time during the method  400  the engine  116  stops running and/or a “key off” event (see step  428  above) occurs, the EMM  350  sends a signal to the sealing valve actuator  320  to close the sealing valve  314 . 
     Turning now to  FIG.  22   , a method  500  for preventing intrusion of water into the combustion chambers  132  of the engine  116  from the exhaust system  156  will be described. The method begins at step  502  following a “key off” condition (step  428 ) occurring. Then at step  504 , the EMM  350  determines if the sealing valve  314  is closed as it is supposed to be. If not, then at step  506  the EMM  350  records a fault and returns to step  504 . It is contemplated that the EMM  350  could then send another signal to reattempt to close the sealing valve  314 . If at step  504  the sealing valve  314  is closed, the EMM  350  goes to sleep. 
     Even though the EMM  350  is in a sleep mode, the exhaust water level sensor  354  is still powered in order to monitor the level of water in the exhaust system  156  at step  508 . If the exhaust water level sensor  354  is tripped (i.e. water reaches the level of the water level sensor  354 ), the water level sensor  354  sends a signal to wake the EMM  350  at step  510 . Then at step  512 , the EMM  350  sends a signal to run the air pump  210 . When it runs, the pump  210  supplies air downstream of the closed sealing valve  314  in an attempt to push the water out of the exhaust system  156 . More specifically, the air pump  210  supplies air upstream of the engine  116 , in the air intake manifold  208  of the air intake assembly  140 . 
     Once the signal to run the air pump  210  is sent at step  512 , the EMM  350  determines if the pressure sensed by the exhaust pressure sensor  356  increases. If the pressure is not increasing, it could be an indication that the pump  210  has failed (i.e. is not running or not running properly) or that there is a leak in the gas flow path between the sealing valve  314  and the water level in the exhaust system  156 , or that the sealing valve  314  is not sealing properly. As such, if at step  514  the pressure is not increasing, then the EMM  350  stops the air pump  210  (not shown), records a fault at step  506  and returns to step  504 . If at step  514  the pressure increases, then the EMM  350  continues to step  516 . It is contemplated that at step  514  the EMM  350  could determine that the pressure is increasing at or above a predetermined rate. 
     At step  516 , the EMM  350  determines based on the signal from the exhaust water level sensor  354  if the water is now at a level below the sensor  354 . If not, the EMM  350  returns to step  512  and the pump  210  continues to run. If the water level is below the water level sensor  354 , then the EMM  350  stops operating the air pump  210  (not shown), goes back to sleep  518 , and the exhaust water level sensor  354  resumes monitoring of the water level. 
     It is contemplated that in addition to running the air pump  210  at step  512 , the EMM  350  could send a signal to the tilt/trim actuator  168  to trim the marine engine assembly  100  up, thus lifting the marine engine assembly  100  partially out of water. It is also contemplated that, if at step  514  the pressure is not increasing, the EMM  350  could send a signal to the tilt/trim actuator  168  to trim the marine engine assembly  100  up, thus lifting the marine engine assembly  100  partially out of water. It is also contemplated that steps  514  and  516  could be omitted and that instead the air pump  210  could be made to run for a predetermined amount of time. It is also contemplated that the air pump  210  could be made to run for a predetermined amount of time at predetermined time intervals even if the exhaust water level sensor  354  has not been tripped. Finally, it is contemplated that the above method could be adapted to use the air pump  210  to remove water from the exhaust system  156  in embodiments where the sealing valve  314  is not provided. 
     If at any time during the method  500  a “key on” event (see step  402  above) occurs, the EMM  350  stops method  500  and begins method  400  at step  302 . 
     Modifications and improvements to the above-described embodiments of the present technology may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting.