Abstract: Several embodiments of turbocharged internal combustion engines wherein the turbocharger is designed to provide high boost at low and mid range and the boost is reduced at high range to maintain either a limitation of the maximum boost or to maintain the boost pressure in a linear relation to engine speed. The means for reducing the boost pressure comprises a throttle valve in the induction passage that is operated in a variety of manners responsive to engine speed.

Abstract: An exhaust gas cleaning system is provided for use with a watercraft engine. A plurality of horizontally positioned exhaust ports are located within an engine cylinder head. An exhaust manifold communicates with each of the exhaust ports at a first end and forms a gas collecting pipe at its second end. The second end of the gas collecting pipe is positioned above the exhaust ports. A generally horizontally positioned exhaust pipe extends from the second end of the gas collecting pipe and continues in a rearward direction. Means are provided for introducing coolant from the engine into the rearwardly extending portion of the exhaust pipe. A removable catalyst member is located within and across the exhaust pipe between the exhaust manifold and the area where coolant is introduced into the exhaust pipe. The catalyst is provided with a plurality of small holes therein, so that exhaust gases may be effectively cleaned.

Abstract: Two embodiments of cylinder head constructions including drain passageways for draining the sealing area of a spark plug of water. In one embodiment, the drain passageway is formed when the cylinder head is cast and in the other embodiment, the drain passageway is machined into the cylinder head.

Abstract: A number of embodiments of marine inboard/outboard drives including an arrangement for sealing the flywheel housing so as to prevent the intrusion of water into it. In all embodiments, a flexible coupling connects the engine flywheel to an input shaft of the outboard drive and this flexible coupling is positioned within the flywheel housing. Various sealing arrangements are incorporated for sealing the opening in the flywheel housing through which the input shaft of the outboard drive extends.

Abstract: An inboard/outboard drive arrangement and specifically an improved exhaust joint therefor wherein at least one of the rigid conduits of the exhaust system is provided with a projection to engage and restrain a hose clamp which may be released and inadvertently dropped so as to prevent loss of the hose clamp into an inaccessible area.

Abstract: Several embodiments of marine propulsion exhaust systems including water lock devices for precluding the entry of water into the engine through its exhaust ports. In each embodiment, the water lock device comprises a control valve that has flow openings for permitting the flow of exhaust gases through the control valve even when the control valve is in its closed position. The flow openings are, however, positioned so as to prevent the flow of water into the engine under these conditions. The openings also create different effective areas so that exhaust pressure tends to open the valve and water pressure tends to close the valve.