Patent ID: 6053785
Filing Date: 2000-04-25
Classification: F01N,F02B,F02M

Abstract:
An outboard motor comprised of a power head consisting an internal combustion engine and a surrounding protective cowling, a drive shaft housing and lower unit depending from said power head and containing a propulsion device for an associated watercraft, an exhaust guide plate underlying said engine at the upper end of said drive shaft housing and lower unit, transmission means for driving said propulsion device from said engine including a drive shaft driven from an engine output shaft and journalled for rotation in said drive shaft housing and lower unit on a longitudinal centerline of said outboard motor, said engine having a plurality of vertically spaced cylinders each having at least one exhaust port for discharging combustion products therefrom, and an exhaust system for discharging exhaust gases from said exhaust port to the atmosphere through a body of water which the associated watercraft is operating under at least some running conditions, said exhaust system including an expansion chamber forming member affixed to the underside of said exhaust guide plate and defining therewith an expansion chamber, an exhaust manifold having inlet ends extending from each of said exhaust ports into said expansion chamber through a single outlet located at a point lying substantially on a longitudinal centerline of said outboard motor and at a forward location therein in substantial alignment with said drive shaft, a trap portion formed in substantial part on the upper side of said exhaust guide plate, said trap portion consisting of an inlet section that extends upwardly from an exhaust outlet opening communicating with said expansion chamber immediately to the rear of said exhaust manifold outlet, a horizontally extending section extending generally transversely to said longitudinal centerline and a downwardly extending section lying to one side of said expansion chamber forming member, said exhaust outlet opening being disposed substantially on said longitudinal centerline and at a rearward location from said exhaust manifold.