Abstract: A system for cooling an engine of a marine propulsion system having an engine and having a cylinder block. An exhaust manifold that conveys hot exhaust gases from the engine and a pump that pumps water from a body of water are also present in the system. A water jacket surrounding the exhaust manifold conveys water from the pump along at least one stream of water having a cross sectional area for cooling the hot exhaust gases in the exhaust manifold. At least one portion of the water jacket includes at least one converging passageway including a wall of the water jacket that tapers inwardly to reduce the cross-sectional area of the stream of water as the water circulates in the water jacket. The pumped water typically has entrained air in the form of air pockets. The converging passageway reduces the air pockets present in the water to provide even cooling of the manifold.

Abstract: A control system for an outboard motor provides an EGR valve and an idle exhaust relief valve which are under the control of a controller that opens and closes the valves as a function of the rotational speed of a crankshaft of the engine. The EGR valve controls the flow of exhaust gas from an exhaust gas conduit to an air intake manifold. The idle exhaust relief valve controls the flow of exhaust gas from the exhaust conduit to a location at atmospheric pressure. In addition, the idle exhaust relief valve is used to allow air to flow from the atmosphere into the exhaust conduit when the engine is turned off.

Abstract: An electrically powered automatic choke system for a turnkey outboard motor has a thermostatic override switch. The automatic choke feature is often not necessary, and sometimes not even desirable, when restarting the engine. The thermostatic override switch prevents the automatic choke from closing carburetor choke shutters when the ambient temperature near the engine under the cowl exceeds a choke deactivation temperature. A switch assembly is provided to retrofit engines on existing outboard motors.

Abstract: An air intake box for a four-stroke marine engine. The air box is generally U-shaped in configuration, including a lower section that is connected to the carburetor throat. The lower section extends forwardly from the carburetor and merges into an upper section via a reverse bend. The upper section extends rearwardly above the carburetor and terminates in a distal inlet end that is located at the rear of the engine. The air box reduces air intake noise, and results in cooler air being supplied to the engine, which enhances combustion.