Abstract: The oil filter device is disposed on a side portion of one side of a cylinder body in a width direction in a cylinder head side with respect to an engine case in a space between center lines of main lubricating oil passages and a cylinder axis line of the cylinder body, and includes an oil pump disposed on the engine case and further lubricating oil passages that connect to the main lubricating oil passage.

Abstract: An engine case includes bearings, an oil pump, lubricating oil passages, and a relief device. The bearings rotatably support a crankshaft and a camshaft. The oil pump and the lubricating oil passages are configured to pressure-feed lubricating oil to the bearings. The relief device is configured to adjust a pressure of the lubricating oil. The lubricating oil passages include main lubricating oil passages. The main lubricating oil passages include communication portions linearly formed with extending portions. The communication portions communicate between the respective bearings of the crankshaft and the camshaft from outside the engine case. The extending portions extend from outside the engine case to the bearing of the camshaft. The relief device is disposed having a relief valve and a relief hole at the extending portions.

Abstract: A lubricating structure for a four-stroke engine includes a first oil groove and a second oil groove. The engine includes a crankcase, a cylinder, a cylinder head and an oil pan. The crankcase makes up a crank chamber. The cylinder head is equipped with a valve chamber housing valve driving mechanism. The oil pan is provided on a bottom of the crank chamber. The first oil groove leads mist of the lubricating oil in the crank chamber to the valve chamber by communicating the crank chamber and the valve chamber with each other. The second oil groove leads surplus lubricating oil in the valve chamber to the oil pan in the crank chamber by communicating a lower part of the valve chamber with a neighborhood of the oil pan in the crank chamber. The first oil groove is set smaller in flow path cross-sectional area than the second oil groove.

Abstract: An axis line of a cylinder and a cylinder head of a four-stroke engine is disposed inclining to one side in a lateral direction with respect to a center line extending in a front-rear direction of the outboard motor from a top view, and a fuel tank is disposed on a side portion of the cylinder and the cylinder head in another side in the lateral direction with respect to the center line.

Abstract: A breather apparatus for an engine includes a breather chamber, one side portion and other side portion of the breather chamber, and a bottom face of the other side portion. The breather chamber is formed, along substantially half a circumference of a cylinder bore, in a cylinder block. The one side portion of the breather chamber is provided with a blow-by gas introduction hole leading blow-by gas in the crank chamber to the breather chamber and a one-way valve opening and closing the blow-by gas introduction hole. The other side portion of the breather chamber has a pipe connection hole connecting a breather pipe to the breather chamber and with a breather oil return passage. The bottom face of the other side portion projects into the crank chamber to a level lower than a bottom face of the one side portion.

Abstract: An axis line of a cylinder and a cylinder head of a four-stroke engine is disposed inclining to one side in a lateral direction with respect to a center line extending in a front-rear direction of the outboard motor from a top view, and a fuel tank is disposed on a side portion of the cylinder and the cylinder head in another side in the lateral direction with respect to the center line.

Abstract: A lubricating structure for a four-stroke engine includes a first oil groove and a second oil groove. The engine includes a crankcase, a cylinder, a cylinder head and an oil pan. The crankcase makes up a crank chamber. The cylinder head is equipped with a valve chamber housing valve driving mechanism. The oil pan is provided on a bottom of the crank chamber. The first oil groove leads mist of the lubricating oil in the crank chamber to the valve chamber by communicating the crank chamber and the valve chamber with each other. The second oil groove leads surplus lubricating oil in the valve chamber to the oil pan in the crank chamber by communicating a lower part of the valve chamber with a neighborhood of the oil pan in the crank chamber. The first oil groove is set smaller in flow path cross-sectional area than the second oil groove.

Abstract: A breather apparatus for an engine includes a breather chamber, one side portion and other side portion of the breather chamber, and a bottom face of the other side portion. The breather chamber is formed, along substantially half a circumference of a cylinder bore, in a cylinder block. The one side portion of the breather chamber is provided with a blow-by gas introduction hole leading blow-by gas in the crank chamber to the breather chamber and a one-way valve opening and closing the blow-by gas introduction hole. The other side portion of the breather chamber has a pipe connection hole connecting a breather pipe to the breather chamber and with a breather oil return passage. The bottom face of the other side portion projects into the crank chamber to a level lower than a bottom face of the one side portion.

Abstract: An axis line of a cylinder and a cylinder head of a four-stroke engine is disposed inclining to one side in a lateral direction with respect to a center line extending in a front-rear direction of the outboard motor from a top view, and a fuel tank is disposed on a side portion of the cylinder and the cylinder head in another side in the lateral direction with respect to the center line.

Abstract: The oil filter device is disposed on a side portion of one side of a cylinder body in a width direction in a cylinder head side with respect to an engine case in a space between center lines of main lubricating oil passages and a cylinder axis line of the cylinder body, and includes an oil pump disposed on the engine case and further lubricating oil passages that connect to the main lubricating oil passage.

Abstract: An engine case includes bearings, an oil pump, lubricating oil passages, and a relief device. The bearings rotatably support a crankshaft and a camshaft. The oil pump and the lubricating oil passages are configured to pressure-feed lubricating oil to the bearings. The relief device is configured to adjust a pressure of the lubricating oil. The lubricating oil passages include main lubricating oil passages. The main lubricating oil passages include communication portions linearly formed with extending portions. The communication portions communicate between the respective bearings of the crankshaft and the camshaft from outside the engine case. The extending portions extend from outside the engine case to the bearing of the camshaft. The relief device is disposed having a relief valve and a relief hole at the extending portions.

Abstract: An outboard motor includes: an engine cover having an upper cover and a lower cover which form an engine room and which can be separated from each other vertically; a ventilation fan for ventilating the engine room; and a fan cover which covers the ventilation fan, the engine cover is configured so that the upper cover is able to be attached to and detached from the lower cover and the lower cover is fixed to an outboard motor main body including an engine, the lower cover has an external air inlet through which to take air into the engine room and a discharge outlet through which to discharge air from the engine room, the fan cover has an air outlet through which to cause air that is sent from the ventilation fan to flow out, and the discharge outlet is connected to the air outlet.

Abstract: An outboard motor includes: an engine cover having an upper cover and a lower cover which form an engine room and which can be separated from each other vertically; a ventilation fan for ventilating the engine room; and a fan cover which covers the ventilation fan, the engine cover is configured so that the upper cover is able to be attached to and detached from the lower cover and the lower cover is fixed to an outboard motor main body including an engine, the lower cover has an external air inlet through which to take air into the engine room and a discharge outlet through which to discharge air from the engine room, the fan cover has an air outlet through which to cause air that is sent from the ventilation fan to flow out, and the discharge outlet is connected to the air outlet.