Outboard motor

摘要

An outboard motor (1) has an engine (10) and a mounting case (50) disposed below and connected to the engine. The mounting case has a depression (51) opening upward. The opening (52) is covered by a cover (56) to form a coolant chamber (58). An exhaust passage (54) passes through the coolant chamber and communicates with an exhaust expansion chamber (67) formed by an extension case (4) to be positioned below the mounting case. The coolant chamber is covered by the cover so that a small mating surface is formed with the coolant chamber independently of an engine mating surface of the mounting case. This simplifies the structure of the mounting case.