Exhaust systems are for outboard marine engines that are configured to propel a marine vessel in a body of water. An intermediate exhaust conduit is configured to receive the exhaust gas from the primary exhaust conduit. A primary muffler receives the exhaust gas from a intermediate exhaust conduit. A secondary muffler receives the exhaust gas from the primary muffler. An idle relief outlet discharges the exhaust gas from the secondary muffler to atmosphere. A bypass valve is positionable into an open position wherein the exhaust gas is permitted to bypass the secondary muffler and flow from the primary muffler to the idle relief outlet and into a closed position wherein the exhaust gas is not permitted to bypass the secondary muffler and instead flows from the primary muffler to the idle relief outlet via the secondary muffler.

An outboard motor having an upper cowling that covers an internal combustion engine, a driveshaft housing located below the upper cowling that covers a driveshaft that is rotated by the internal combustion engine, a transmission housing that is located below the driveshaft housing and covers a transmission that is operably connected to the driveshaft, and a lower gearcase that is located below the transmission housing and covers a set of angle gears that operably connect the transmission to a propulsor for imparting a propulsive force in a body of water.

An internal combustion engine for an outboard motor comprises a cylinder block having first and second banks of cylinders that extend transversely with respect to each other in a V-shape so as to define a valley there between. An exhaust manifold conveys exhaust gas from the internal combustion engine and is at least partially disposed in the valley. A supporting mechanism supports the exhaust conduit with respect to the internal combustion engine. The supporting mechanism is configured to allow the exhaust conduit to move with respect to the internal combustion engine in 360 degrees in a plane defined by the lateral and transverse axes, and laterally towards and away from the internal combustion engine, thereby facilitating assembly of the exhaust manifold and the internal combustion engine despite positional tolerance differences there between.

An outboard motor that significantly reduces or prevents discoloration around an exhaust hole includes an engine, a drive shaft, a propeller shaft, a housing, a discharge passage, and non-metal covers. The housing includes a discharge outlet to discharge an exhaust gas of the engine and the cooling water of the engine. The discharge passage guides the exhaust gas and the cooling water from the engine toward the discharge outlet. The covers are detachably attached to the housing so as to cover the discharge outlet and include at least one exhaust opening.

A marine engine assembly has a housing including an outer housing having a front wall, an inner housing disposed in the outer housing and being connected to the outer housing by at least one housing fastener disposed at at least one first position, a cover removably connected to the outer housing, and a gearcase connected to a lower portion of the outer housing. An internal combustion engine has a front face connected to and supported by the inner housing by at least one engine fastener disposed at at least one second position being different from the at least one first position, and a crankshaft defining a crankshaft axis intersecting the front wall of the outer housing. The inner housing is disposed at least in part between the front face of the internal combustion engine and the front wall of the outer housing.

An outboard-motor vibration-isolating cooler system apparatus providing a retrofit substitute for the midsection and the lower unit of a standard outboard motor, having a substitute closed-loop cooling system with an exterior heat exchanger, a substitute oil reservoir, a substitute exhaust system, and a substitute propulsion system with an isolating power-take-off shaft, allowing an existing standard outboard-motor powerhead to be used in conditions not conducive to standard open-loop water cooling, such as shallow-water, muddy-water, obstructed-water, seawater, or corrosive-water conditions.

THIS invention relates to a propeller and more particularly, but not exclusively, to a propeller for use with inboard and outboard boat engines. The propeller includes a hollow hub and a plurality of primary blades extending substantially radially outwardly from the hub, with each primary blade including a blade face, a blade back and a root section. The propeller is characterized in that a set of secondary blades are provided inside the hub, and that an inner volume of the hub is in flow communication with a volume radially outwardly of the propeller hub.

Disclosed is an outboard motor including an exhaust manifold having a plurality of first openings connected to exhaust ports to form a first passage vertically extending, and an exhaust passage having a second passage extending upward along the exhaust manifold, a third passage that is connected to an upper end portion of the second passage and passes over the exhaust manifold, a fourth passage that is connected to the third passage, turns over to the downside, and then extends downward along the exhaust manifold, so that a lower end portion thereof communicates with a fifth passage provided in the engine holder, the second, third, and fourth passages being arranged in one side of the left-right direction of the cylinder block, wherein the exhaust passage is arranged in a swirling shape, and an exhaust gas cleaning catalyst is installed in a middle portion of the second passage.

[Problem] To perform an assembling operation easily while attaining improvement in engine efficiency. [Solution] An outboard motor 10 according to the invention includes an upstream side duct 42 which is fixed to an engine upper cover 27, and a downstream side duct 43 which is fixed to an engine 14 side. The upstream side duct 42 includes an exhaust port 52 which is opened at its side face. The downstream side duct 43 includes a downstream side lower duct 59 and a downstream side upper duct 60. In the downstream side lower duct 59, a suction port 61 is provided at a position opposed to the exhaust port 52 and separately at a predetermined distance from the exhaust port 52. In the downstream side upper duct 60, an exhaust port formed toward a throttle body 36 of the engine 14 is provided above the downstream side lower duct 59. The upstream side duct 42 and the downstream side duct 43 are formed so as not to interfere with each other when the engine upper cover 27 is moved vertically.

Marine engine includes a cylinder block having first and second banks of cylinders that are disposed along a longitudinal axis and extend transversely with respect to each other in a V-shape so as to define a valley therebetween. A catalyst receptacle is disposed at least partially in the valley and contains at least one catalyst that treats exhaust gas from the marine engine. A conduit conveys the exhaust gas from the marine engine to the catalyst receptacle. The conduit receives the exhaust gas from the first and second banks of cylinders and conveys the exhaust gas to the catalyst receptacle. The conduit reverses direction only once with respect to the longitudinal axis.