An outboard motor comprising: an engine; a drive shaft extending from the engine in a first direction; a propeller shaft extending in a second direction intersecting with the drive shaft; a propeller connected to the propeller shaft; the propeller configured to generate a forward propulsive force in a forward direction along the second direction and configured to generate a backward propulsive force in a backward direction along the second direction; a housing configured to accommodate the engine, the drive shaft, and the propeller shaft and forming a discharge chamber, the discharge chamber configured to discharge exhaust gas of the engine; a first passage configured to guide the exhaust gas from the engine to the discharge chamber inside the housing; a second passage configured to guide water to the discharge chamber, the outboard motor configured such that the water enters the housing when the forward propulsive force is generated; and a valve structure (40, 50) configured to regulate or permit passage of the exhaust gas at a first connection (131c, 59a) by exhaust pressure and water pressure, the first connection (131c, 59a) connecting the first passage and the discharge chamber, the outboard motor configured such that the exhaust pressure acts from the first passage toward the discharge chamber, the water pressure acts from the second passage toward the discharge chamber; the valve structure (40, 50) is configured to regulate the passage of the exhaust gas at the first connection (131c, 59a) by the water pressure, when the forward propulsive force is generated; and the valve structure (40, 50) is configured to permit the passage of the exhaust gas at the first connection (131c, 59a) by the exhaust pressure, when the backward propulsive force is generated, wherein the housing includes a water intake portion; the water intake portion is configured and provided to take the water into the second passage when the forward propulsive force is generated; the water intake portion includes an opening; and at least a part of the opening opens forward in the forward direction along the second direction. an engine; a drive shaft extending from the engine in a first direction; a propeller shaft extending in a second direction intersecting with the drive shaft; a propeller connected to the propeller shaft; the propeller configured to generate a forward propulsive force in a forward direction along the second direction and configured to generate a backward propulsive force in a backward direction along the second direction; a housing configured to accommodate the engine, the drive shaft, and the propeller shaft and forming a discharge chamber, the discharge chamber configured to discharge exhaust gas of the engine; a first passage configured to guide the exhaust gas from the engine to the discharge chamber inside the housing; a second passage configured to guide water to the discharge chamber, the outboard motor configured such that the water enters the housing when the forward propulsive force is generated; and a valve structure (40, 50) configured to regulate or permit passage of the exhaust gas at a first connection (131c, 59a) by exhaust pressure and water pressure, the first connection (131c, 59a) connecting the first passage and the discharge chamber, the outboard motor configured such that the exhaust pressure acts from the first passage toward the discharge chamber, the water pressure acts from the second passage toward the discharge chamber; the valve structure (40, 50) is configured to regulate the passage of the exhaust gas at the first connection (131c, 59a) by the water pressure, when the forward propulsive force is generated; and the valve structure (40, 50) is configured to permit the passage of the exhaust gas at the first connection (131c, 59a) by the exhaust pressure, when the backward propulsive force is generated, wherein the housing includes a water intake portion; the water intake portion is configured and provided to take the water into the second passage when the forward propulsive force is generated; the water intake portion includes an opening; and at least a part of the opening opens forward in the forward direction along the second direction.