Patent ID: 8328590

Claim:
An outboard motor having an internal combustion engine with a combustion chamber, said outboard motor comprising: an upstream intake silencer receiving intake air for combustion; and a downstream intake silencer through which the intake air from the upstream intake silencer flows into the combustion chamber; wherein the upstream intake silencer and the downstream intake silencer are disposed such that the upstream intake silencer is superposed above the downstream intake silencer, the upstream intake silencer has an upstream inlet passage, an upstream expansion chamber and an upstream outlet passage, the downstream intake silencer has a downstream inlet passage connected to the upstream outlet passage, a downstream expansion chamber and a downstream outlet passage, the upstream expansion chamber has a lower wall of a stepped shape including a raised part which overlaps the downstream intake silencer in a plane and a lowered part which extends without overlapping with the downstream intake silencer in a plane and at a level lower than that of the raised part, and the upstream inlet passage and the upstream outlet passage of the upstream intake silencer are formed in the lowered part and the raised part of the lower wall, respectively, wherein an air-intake space for introducing external air extends below and along the lower wall of the upstream expansion chamber and is connected to the upstream inlet passage of the upstream expansion chamber to supply the external air into the upstream inlet passage, and wherein the downstream expansion chamber has a stepped upper wall including a raised part and a lowered part which underlies the lower wall of the upstream expansion chamber in a plane and which extends at a level lower than that of the raised part of the stepped upper wall, and the downstream inlet passage is formed in the lowered part of the upper wall.