Exhaust system for outboard motor

摘要

An outboard motor includes a housing unit mounted on an associated watercraft. An engine is disposed above the housing unit. The engine defines a first exhaust passage communicating with a combustion chamber of the engine. The housing unit defines a second exhaust passage communicating with the first exhaust passage. The second exhaust passage communicates with outside through at least an underwater exhaust discharge port formed at a portion of the housing unit. An air intake device communicates with either the first exhaust passage or the second exhaust passage. The air intake device includes a one-way valve that allows air to enter the first or second exhaust passage and inhibits exhaust gases from moving beyond the one-way valve.