The present invention is an exhaust system for an engine. More particularly, the invention is an exhaust system for an internal combustion engine powering a water propulsion device of a watercraft.
Watercraft are often powered by internal combustion engines. This is especially true of the type of watercraft known as personal watercraft.
Personal watercraft have a hull which defines an engine compartment. The engine is mounted in the engine compartment and has its output shaft arranged to drive a water propulsion of the watercraft.
The engine produces exhaust products as a by-product of the combustion of fuel. It is desirable to route this exhaust from the engine to a point external to the watercraft. Generally, an exhaust system is provided for this purpose. The exhaust system normally includes at least one exhaust pipe extending from a port through the engine leading from a cylinder to a discharge point.
Many times, little attention is given the exhaust system, with the result being a detrimental affect on engine and/or watercraft performance. For example, it is generally desirable to arrange the exhaust system so that it occupies a small amount of space. In this manner, the space occupied by the engine is minimized, and the overall size of the watercraft may be minimized, lending to a light and maneuverable craft. In many instances, however, this compact arrangement results in the exhaust system having sharp turns or bends which restrict the flow of exhaust therethrough. The exhaust gas back-pressure reduces engine power, especially in two-cycle engines.
An associated problem is that when the engine has multiple cylinders, a compact exhaust system may result in the exhaust flow path corresponding to one cylinder to be different than another cylinder. When the exhaust flow paths for cylinders vary, the operating temperature of the cylinders tends to vary. The cooling and air/fuel charging needs of the cylinders then varies, complicating the design and/or operating conditions of the engine.
Also, exhaust systems for engines powering watercraft are subjected to forces which many other engines are not, especially watercraft vibration. These vibration forces have the tendency to reduce the life of the exhaust system, especially exhaust system mufflers.
An exhaust system for an engine powering a watercraft which overcomes the above-stated problems is desired.
The present invention is an exhaust system for an engine powering a personal watercraft. Preferably, the personal watercraft is of the type having a hull and a front end and a rear end. The personal watercraft has a water propulsion device which is preferably positioned near a rear end of the hull.
The engine comprises a multi-cylinder engine in the hull which drives the water propulsion device in the preferred form of a jet pump mounted in the hull to power the personal watercraft. The engine includes a crankcase, crankshaft and cylinders. The cylinders each having an individual exhaust manifold pipe connected to an exhaust port of each cylinder and extending rearwardly of the crankshaft from the exhaust ports. The multiple exhaust manifold pipes are coupled together at their downstream ends at a point vertically above said crankcase to form a single.