Exhaust system for outboard motor

An outboard motor comprising an internal combustion engine, a housing unit disposed below the engine, an exhaust system configured to guide exhaust gases from the engine, the exhaust system including a main exhaust passage and an idle exhaust passage, the main exhaust passage being configured to discharge exhaust gases produced at engine speeds above idle to the body of water through the housing unit, the idle exhaust passage being configured to discharge exhaust gases produced during idle engine speeds to the atmosphere, an exhaust guide member defining a portion of the main exhaust passage, the exhaust guide member forming a recessed area in the main exhaust passage portion, and an exhaust conduit communicating with the main exhaust passage portion to form a further portion of the main exhaust passage downstream from the main exhaust portion defined by the exhaust guide member, the idle exhaust passage being branched from the main exhaust passage portion at the recessed area and proximate to the exhaust conduit.

An outboard motor comprising an internal combustion engine, a housing unit disposed below the engine, an exhaust system configured to guide exhaust gases from the engine, the exhaust system including a main exhaust passage and an idle exhaust passage, the main exhaust passage configured to discharge exhaust gases produced at engine speeds above idle to the body of water through the housing unit, the idle exhaust passage configured to discharge exhaust gases produced during idle engine speeds to the atmosphere, and an exhaust guide member defining a portion of the main exhaust passage, the idle exhaust passage being branched from the main exhaust passage portion, the idle exhaust passage extending at an acute angle relative to a direction of exhaust gas flow in the main exhaust passage.

An outboard motor comprising an internal combustion engine, a housing unit disposed below the engine, an exhaust system configured to guide exhaust gases from the engine, the exhaust system including a first exhaust passage and a second exhaust passage, the first exhaust passage configured to discharge exhaust gases to the body of water through the housing unit at relatively high engine speeds, the second exhaust passage configured to discharge exhaust gases to the atmosphere at relatively low engine speeds, and a support member arranged to support the engine, the support member defining a portion of the first exhaust passage, the support member forming a recessed area in the first exhaust passage portion, the second exhaust passage being branched from the first exhaust passage portion at the recessed area and at a location relatively distal from the engine.

A method for forming an exhaust guide member of an outboard motor, the exhaust guide member defining a main exhaust passage and a secondary exhaust passage branched from the main exhaust passage within the exhaust guide member, the method comprising placing a first mold in a cast frame of the exhaust guide member, placing a second mold in the cast frame, casting the exhaust guide member, removing the first mold from the cast frame, removing the second mold from the cast frame in a direction opposed to a direction in which the first mold is removed, and boring an aperture in a recessed area formed by one of the first or second molds.