Marine exhaust valving

Abstract

A marine engine exhaust system includes a catalyst arranged to intercept a flow of exhaust flowing along the exhaust system, a water muffler downstream of the catalyst, and a water-activated exhaust valve disposed between the water muffler and an upstream catalyst and configured to impede flow of water upstream from the muffler to the catalyst.

1 . An engine exhaust system comprising:
 a catalyst arranged to intercept a flow of exhaust flowing along the exhaust system;   a water muffler downstream of the catalyst; and   an exhaust valve disposed upstream of the water muffler and configured to impede water flow.   
     
     
         2 . The exhaust system of  claim 1  further comprising an exhaust manifold, and wherein the catalyst is disposed downstream of the exhaust manifold. 
     
     
         3 . The exhaust system of  claim 2 , wherein the exhaust manifold is water-jacketed. 
     
     
         4 . The exhaust system of  claim 1  further comprising a water injection elbow downstream of the catalyst, the injection elbow defining a water inlet into which water is injected into the flow of exhaust. 
     
     
         5 . The exhaust system of  claim 4 , wherein the exhaust valve is disposed downstream of the injection elbow. 
     
     
         6 . The exhaust system of  claim 1  mounted in a boat and further comprising an exhaust outlet at which the flow of exhaust is dispersed into atmosphere outside the boat above a water line. 
     
     
         7 . The exhaust system of  claim 6 , including an exhaust passage extending from the water lift muffler to the exhaust outlet and extending above the exhaust outlet. 
     
     
         8 . The exhaust system of  claim 1 , wherein the water lift muffler includes a drain. 
     
     
         9 . The exhaust system of  claim 1  further comprising a water level indicator. 
     
     
         10 . The exhaust system of  claim 9 , wherein the water level indicator is disposed between the water lift muffler and the catalyst and is responsive to rising water level to generate a warning signal. 
     
     
         11 . The exhaust system of  claim 1 , wherein the exhaust valve comprises a float valve. 
     
     
         12 . The exhaust system of  claim 1 , wherein the exhaust valve comprises a ball valve having a ball floatable on a rising water level to close the valve. 
     
     
         13 . The exhaust system of  claim 1 , wherein the catalyst is configured to simultaneously reduce oxides of nitrogen, carbon monoxide and hydrocarbons. 
     
     
         14 . The exhaust system of  claim 1 , wherein the catalyst is configured to reduce carbon monoxide to between about  9  parts per million and 30 parts per million. 
     
     
         15 . The exhaust system of  claim 1 , wherein the exhaust valve is water-activated.