Patent ID: 8083558
Filing Date: 2011-12-27
Classification: F02M

Abstract:
1. An outboard motor comprising: an internal combustion engine; an intake system for carrying intake air for combustion into a combustion chamber formed in the internal combustion engine; an engine cover forming an engine compartment for enclosing the internal combustion engine; and a top cover covering the engine cover from above, wherein the outboard motor includes an air-intake opening formed outside the engine compartment, and an intake silencer for carrying intake air taken in through the air-intake opening into the intake system, the intake system being disposed within the engine compartment; wherein the intake silencer is disposed outside the engine compartment, is spaced apart from the engine cover such that an air-intake space connecting to the air-intake opening is formed between a top wall of the engine cover and the intake silencer; and the intake silencer has an entrance duct spaced apart from the top wall and having an upstream end through which intake air flows from the air-intake space into the entrance duct, a wall structure defining an expansion chamber into which intake air flows through the inlet air passage, and an exit duct forming an outlet air passage through which intake air flows from the expansion chamber into the intake system; wherein the inlet air passage has an upstream end opening into the air-intake space, and is on a rear side of a downstream end of the outlet air passage and at a level higher than that of the air-intake opening; and the entrance duct does not extend downward from a bottom wall included in the wall structure defining the expansion chamber and extends upward from the bottom wall in the expansion chamber, wherein the intake system further includes a downstream intake silencer into which intake air flows through the outlet air passage of the exit duct; the downstream intake silencer has a downstream expansion chamber, a vertically extending inlet air passage opening into an upper part of the downstream expansion chamber, and a horizontally extending outlet air passage formed above a bottom wall forming the downstream expansion chamber; the downstream expansion chamber has a lower extension extending to a level below that of the outlet air passage; and a horizontal water-stopping rib is disposed between the lower extension and the outlet air passage.