An outboard propulsion system comprising a first portion for attachment to a boat, wherein the first portion is fixed about a substantially vertical axis, and a second portion connected to the first portion and configured to rotate about a steering axis, wherein the first portion comprises a sealed housing enclosing a member having a longitudinal axis relative to which it may move and the second portion comprises a gear configured to engage with the member such that movement of the member relative to its longitudinal axis generates rotational movement of the gear about the steering axis, and wherein the sealed housing comprises a sensor configured to determine the position of the member within the sealed housing.

An exhaust pipe has an upstream-side exhaust pipe extending downward from an engine to house a catalyst for exhaust gas purification, and a downstream-side exhaust pipe located downstream of the upstream-side exhaust pipe, and extending upward from the catalyst and then bending downward. Under a configuration in which an exhaust pipe is disposed below an engine, with a simple configuration, a catalyst is hardly exposed to water.

A V-type engine in which exhaust pipe arrangement is easily performed even in a V-type engine and that can be downsized even when a catalyst is installed. The engine has cylinders where pistons operate are arranged in a V-shape, a crankshaft driven by the driving of the pistons is disposed vertically, exhaust pipes communicating with exhaust openings in the respective banks of a cylinder head are included, merging exhaust pipes (exhaust pipes) in the respective banks are drawn toward a side of the cylinder head to be merged, and a catalyst holder that holds a catalyst is provided in a merge portion of the merging exhaust pipes. In this manner, since the merging exhaust pipes in the respective banks are merged and the catalyst holder is provided in this merge portion, exhaust gas from each bank can be purified by the catalyst.

An engine for an outboard motor is provided with an engine body, an intake system configured to supply combustion air to the engine body, an exhaust passage formed by connecting the engine body and middle and lower units thereunder, a catalyst provided in the exhaust passage, and an air pump configured to supply secondary air to an upstream side of the catalyst. The intake system is arranged in a side portion of one side of the left or right side of the engine body, and the exhaust passage and the air pump are arranged in a side portion of the other side of the left or right side of the engine body.

An exhaust apparatus of an outboard motor equipped with a four-stroke engine includes an exhaust pipe having a cylindrical shape and being connected to an exhaust passage of an engine holder, wherein the exhaust pipe is disposed in an exhaust passage of the exhaust manifold in a manner being erected upright in parallel to the crankshaft, and the exhaust pipe has an upper end opened in an upper portion of the exhaust passage and a lower end supporting the cylinder block, and the exhaust manifold and the exhaust pipe are provided with a gap therebetween in a plan view acting as an exhaust collection space adapted to collect exhaust gas from the exhaust manifold.

An eight cylinder engine includes cylinders that are fired at intervals corresponding to a crank angle of 90 degrees. The firing is conducted in four cylinders of each of first and second banks at uneven intervals. In a pair of cylinders of each of the banks in which the firing is consecutively conducted at an interval corresponding to a crank angle of 90 degrees, a central angle of an exhaust cam provided for one cylinder in which the firing is conducted later is larger than that of an exhaust cam provided for the other cylinder. In a pair of cylinders of each of the banks in which the firing is consecutively conducted at an interval corresponding to a crank angle of 270 degrees, a central angle of an exhaust cam provided for one cylinder in which the firing is conducted later is larger than that of an exhaust cam provided for the other cylinder.

An engine includes an exhaust sensor projecting from an opening in an inner surface of a first exhaust pipe to inside of an exhaust passage, and a projection provided in the inner surface of the first exhaust pipe along the opening, and positioned farther inside the exhaust passage than the opening, wherein at least a portion of the projection is positioned upstream of the opening in a flow direction of exhaust gases.

An engine includes a V-shaped cylinder body, first and second exhaust manifolds inside a V-shaped line, and an exhaust pipe. The exhaust pipe includes a first upstream end portion into which exhaust gases discharged from first cylinders to the first exhaust manifold flow, and a second upstream end portion into which exhaust gases discharged from second cylinders to the second exhaust manifold flow. A spiral wound gasket seals a gap between the first exhaust manifold and the first upstream end portion.

An intake system is arranged in a side portion of one side of an engine body in a left-right direction, and the exhaust passage and the air pump are arranged in a side portion of the other side of the cylinder block and the cylinder head of the engine body in the left-right direction.

Disclosed is an outboard motor including an exhaust manifold having a first passage that is provided with a plurality of first openings connected to a plurality of exhaust ports and extends vertically, and a second passage that is arranged under the first passage and has a second opening provided in a lower end portion and connected to a third passage formed in the engine holder. The first and second passages of the exhaust manifold are formed integrally, and the exhaust manifold is formed separately from the cylinder head and the cylinder block and is detachably installed.