Abstract: A back draft carburetor of the type in which a vacuum source in the throat of a carburetor is communicated to the air space above the fuel in the float bowl of the carburetor includes a valve disposed between the vacuum source and the float bowl. At low vacuum levels in the carburetor throat, the valve is in a closed position in which the vacuum in the carburetor is sealed off from the float bowl. Upon sensing a higher vacuum level, the valve moves to an open position which allows the vacuum in the carburetor throat to be communicated to the air space in the float bowl.

Abstract: In a two cycle internal combustion engine (2) having a cylinder liner (14), a fuel-air flow passage (52) is provided from the crankcase (8) to the exhaust bridge (38) in the cylinder liner (14) and the exhaust bridge (39) in the cylinder block (12) along the interface between the cylinder liner (14) and the cylinder block (12). A plurality of apertures (57-60) are provided through the cylinder liner (14) communicating with the fuel-air flow passage (52). A second fuel-air flow passage (56) is provided between the piston (4) and the cylinder liner (14) and in communication with the apertures (57-60) to facilitate fuel-air mixture flow through the exhaust bridge (38) to improve lubrication and cooling thereof.

Abstract: In a two cycle internal combustion engine (2), a fuel-air flow passage and reservoir (52) is provided along the exhaust bridge (34) and between the piston (4) and the cylinder inner wall (36) for lubricating the exhaust bridge (34). The piston (4) has a flat spot (50) machined on its side wall (38) to form an axially extending flow passage and reservoir closed at its top end by the piston rings (40) and at its bottom end by a lower portion (60) of the piston side wall (38) which is not machined and which is closely adjacent the cylinder inner wall (36). When the piston (4) is in its power stroke, crankcase pressure forces fuel-air mixture through holes (56, 58) in the piston side wall (38) at the flat surface (50) into the flow passage and reservoir (52). If the exhaust bridge (34) heats and expands into the cylinder (6), the piston (4) will not rub on it.

Abstract: In a two cycle internal combustion engine (2), a fuel injection system is provided with a low profile compact intake manifold (22) mounted to the crankcase (8) by an adaptor plate (24) and defining an intake air flow path in a first direction (28) behind the manifold (22) through a gap between the manifold (22) and the crankcase (8) provided by the adaptor plate (24). Intake air then flows (32) into throttle bore passages (30) from behind the manifold and then reverses direction and flows through supply passages (34) having fuel injectors (38) and then into the crankcase (8). The passages share a common plenum (42) within the manifold. The fuel injectors (38), their electrical connectors (48) and a common rigid fuel supply rail (44) are all in the common plenum (42) entirely within the low profile manifold (22) and sealed from moisture and salt in a marine environment.

Abstract: A cooling system for the engine (11) of an outboard motor (10) uses a pressure relief valve (28) to control the coolant pressure and flow through the cylinder block (34). The relief valve member (36) controls flow at the outlet (42) of the block and is controlled by a diaphragm (45) responding to pump (14) discharge pressure at the inlet to the block (34). An orifice (53) bypasses flow around the block (34) when the main valve seat (35) is closed and is closed by the valve member (36) when the main valve seat (35) is fully opened.

Abstract: In a two cycle internal combustion engine (2) wherein heavy fuel ends accumulate in lower portions of the crankcase (8), recirculation means (36, 38) are provided for variably recirculating the heavy fuel ends back into the crankcase only at higher engine speeds for subsequent combustion. The heavy fuel ends are collected in a reservoir (36), and held therein at idle, to minimize engine smoke. The heavy fuel ends are released from the reservoir at higher engine speed for recirculation through a delivery line (40) which is selectively exposed by a throttle valve (24) to crankcase vacuum only at higher engine speed, whereby the heavy fuel ends are sucked from the reservoir through the delivery line and carburetor throat (26) into the crankcase.

Abstract: In a two cycle internal combustion engine having a water cooling system with a water valve (4) spring biased (64) to a normally closed condition and opened by water pressure in the engine block (14) to permit passage of water out of the block to a radiator or the like for increased cooling, an improvement is provided for keeping the water valve closed at idle without increased spring pressure such that the water valve remains closed at idle, notwithstanding block pressure, and thus enables the engine to warm up, and such that the water valve opens at higher engine speeds to afford proper cooling and prevent abnormally high water pressure in the block which would otherwise be caused by increased spring pressure. Engine crankcase pressure (6) is continually provided (24) to the valve to aid spring biased closing thereof.

Abstract: A marine propulsion system is provided with a valve (2) for automatically mixing fuel and oil for a two cycle crankcase compression internal combustion engine. The valve operates on a pressure differential, such as that supplied from the suction intake vacuum side of a fuel pump. Fuel is alternately and cyclicly directed by a transitioning shuttle spool valve (50) through respective transfer passages (34, 38) to opposite sides of a diaphragm (24) to drive the diaphragm in reciprocal movement such that in a first half cycle the diaphragm is driven in one direction and expels fuel from its one side, and in the second half cycle the diaphragm is driven in the other direction and expels fuel from its other side. A plunger (48) operatively couples the diaphragm to the directional shuttle spool valve through spring biased lost motion detent means (52). The directional shuttle spool valve is actuated between its alternate positions near the end of the plunger travel stroke in each direction.

Abstract: A gear drive for driving accessories such as an oil pump for a two-cycle engine (10) includes a worm member (25) mounted on the crankshaft (14) of the engine. The worm member (25), formed of a low friction plastic material such as nylon impregnated with molybdenum disulfide, engages a worm gear (24) mounted on the engine (10) to drive the oil pump (21).

Abstract: A hydraulic system for trimming and tilting an outboard propulsion unit (10) includes both trim piston-cylinder units (22, 23) and a trim-tilt piston-cylinder unit (17). The flow of hydraulic fluid from the reversible pump (49) is controlled by a spool valve (26). A pressure relief valve (71) is mounted in the spool (50) to maintain pressure on one side of the spool (50) when the pump (49) is turned off to rapidly close the return valve (56) and prevent further movement of the piston-cylinder units.

Abstract: A hydraulic trim-tilt system 15 for an outboard motor 10 includes a hydraulic trim-tilt piston-cylinder unit 16 pivotally connected to both the transom bracket 11 and the swivel bracket 12. Hydraulic trim piston-cylinder units 22 are mounted in the transom bracket 11. A pilot operated check valve 43 mounted in the piston 38 of one of the trim piston-cylinder units 22 serves to limit the maximum pressure in the system when the trim piston-cylinder units 22 have reached the end of their stroke.

Abstract: The invention provides a remote oil tank (19) to supply oil to an oil reservoir (29) mounted on a two-cycle, crankcase compression engine (10) such as used for outboard motors. Crankcase pressure may be used to pressurize the remote tank (19) to move the oil.

Abstract: A cold start fuel enrichment system for an internal combustion engine uses fuel from the upper carburetor for enriching the air-fuel mixture in the lower carburetors by gravity feed. A fuel line runs from the upper carburetor float bowl to the throttle bores of the lower carburetor. A solenoid valve in the fuel line controls its operation.