Patent ID: 8177593
Filing Date: 2012-05-15
Classification: B63H,F01N,Y02T

Abstract:
1. An outboard motor comprising: an engine including an exhaust port; an exhaust passage including a first upstream end connected to the exhaust port of the engine, and a first downstream end arranged to open underwater; an idle exhaust passage including a second upstream end connected to the exhaust passage, and a second downstream end arranged to open to atmosphere; a contraction portion and an expansion chamber provided in the idle exhaust passage and arranged to reduce exhaust noise; a bypass passage including a third upstream end connected to the idle exhaust passage at a downstream side relative to the contraction portion and the expansion chamber, and a third downstream end connected to the idle exhaust passage at an upstream side relative to the contraction portion and the expansion chamber; and a check valve provided in the bypass passage and arranged such that air flows only from the third upstream end to the third downstream end.