Abstract: Inversion-protection of an outboard marine engine is achieved by fitting inside the engine casing watertight boxes to enclose the water-sensitive electrical components, i.e. the engine starter solenoid and the power pack. The starter motor spindle is provided with a shaft seal and the engine exhaust is fitted with an exhaust pipe in the form of a vertical hairpin or U-tube. The engine air intake box has fitted inside it a horizontally sliding valve that is automatically closed by a vertically-sliding weighted wedge engaging the valve rod.

Abstract: A marine outboard motor is provided with an exhaust valve assembly to operate automatically and prevent ingress of water in the event of a capsize. The exhaust gases pass downward through a vertical tube, to a ring of exhaust ports in the tube wall and, if the engine is inverted, a weighted sleeve fitted telescopically round the lower end of the tube drops into a position where it closes the exhaust ports in a fluid-tight manner. Inside the tube is a check-valve in the form of a captive ball, that upon inversion, drops on to a valve seat located above the ring of exhaust ports.