Four cycle engine for a marine propulsion system

摘要

A marine engine is made with a head portion that includes an exhaust manifold that is formed as an integral part of the head portion during a lost foam casting procedure. The head portion comprises a plurality of combustion chambers in which each combustion chamber has at least one exhaust throat that connects the combustion chamber in fluid communication with at least one exhaust port. All of the exhaust ports connect associated combustion chambers in fluid communication with an exhaust manifold that is formed integrally within the head portion during the initial lost foam casting process. An exhaust outlet opening from the exhaust manifold is positioned above at least one exhaust port of at least one combustion chamber to form a water trap or stand pipe that inhibits water ingestion under certain adverse conditions. Water passages and oil passages are formed integrally within the head portion during the lost foam casting process. The head portion of the present invention reduces the number of components needed to provide the functions of the cylinder head portion and, as a result, improves reliability and reduces cost.