Abstract: A hydraulic trim-tilt system for an outboard motor (10) utilizes a first pilot operated relief valve (48) in one trim piston (21) to limit the stroke of the trim pistons (21, 22) under load. After the trim pistons have reached the top of their stroke, under reduced load, the first pilot operated relief valve (48) is blocked and a second pilot operated relief valve (58) operates to allow a higher pressure to be supplied to the trim-tilt unit (16) to lift the outboard propulsion unit (15) in a higher shallow water drive range.

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: An exhaust system for an outboard motor (10) includes a main exhaust passageway (16) extending through a partially water filled chamber (17) in the drive shaft housing (13). An inlet idle relief passage (23) connects the top of the chamber (17) with the main exhaust passageway (16) and an outlet passage (24) connects the top of the chamber (17) with the atmosphere. The system thus defines an effective exhaust silencer for the idle exhaust.

Abstract: An adjustment is provided for the friction between a throttle hand grip (12) and the steering arm (10) of an outboard motor. An internal cam surface (32) in knob (15) will press against a corresponding external cam surface (31) on the throttle control handle (19) to allow adjustment of the friction between the throttle control handle (19) and the steering arm tube (17) by rotating the knob (15).

Abstract: A locking device (15) for preventing loosening of the clamp screw (13) and removal of the clamp bracket (11) of an outboard motor from the transom (10) of a boat. The locking device (15) has a tubular member (16) with holes (20, 21, 22) to accommodate the clamp handle (14), an arm of the clamp bracket (11), and a padlock (17). The tubular member (16) fits coaxially over the clamp screw (13) to protect the screw.

Abstract: A marine propeller mounting arrangement includes a sleeve member (14) for mounting on a propeller shaft (11), a propeller (10) having an inner hub (17) which fits over the sleeve member (14) and a cushion member (16) fitting between the sleeve member (14) and the propeller inner hub (17). The sleeve member (14) includes radially extending projections (26) registering with channels (31) in the hub to positively drive the propeller (10), even in the event of failure of the cushion member (16). The propeller (10) has an outer hub (28) surrounding the inner hub (17) to define an exhaust gas passageway through the propeller (10).

Abstract: An outboard motor (10) is supported on a boat by a swivel bracket (12) mounted for tilting movement on a transom bracket (11). A shallow water tilt mechanism is provided by a shallow drive bracket (29) controlled by a lever (30) mounted on the swivel bracket (12). The lever (30) is linked to the shallow drive bracket (29) by a double acting torsion spring (38) which allows the operator to set the lever (30) for the desired position of the shallow drive bracket (29). Subsequent tilting movement of the swivel bracket (12) allows the shallow drive bracket to assume the preselected position.

Abstract: Water inlets (16) are formed on the sides of the gearcase (13) of a marine propulsion unit. Ramps (26) and (27) are formed in the gearcase (13) ahead of the inlets (16) to direct flow to the inlets (16). The ramp (26) ahead of the upper ports (16) has a greater depth to provide a substantial flow of water at positive pressure, while the ramp (27) ahead of the lower ports (16) has a lesser depth to avoid disturbances in flow when the unit is operated at high speeds where the upper inlets (16) are normally above the resting surface of the water.

Abstract: A coupling assembly (17) for coupling the crankshaft (18) of an inboard engine (11) to the input shaft (19) of an outboard propulsion unit (15) has a coupling member (21) stamped from steel. The coupling member (21) is attached to the engine flywheel (20) at three points at the vertices of the triangular coupling member base. An elastomeric annulus (23) couples the coupling member (21) to the input shaft (19).

Abstract: A latch for the cowl of an outboard motor engine (13) includes a catch (15) mounted on one of the cowl member (12). A lever (19) is pivotally attached to the other cowl member (11) and a resilient spring member (22) is pivotally attached to the lever (19). The lever (19) and spring member (22) act to provide an overcenter action on the lever (19) when the latch is closed. The lever (19) includes a shield (29) to conceal the latch assembly.

Abstract: A flushing device (12) is provided to supply water to an inlet (18) provided on the bottom of the anti-ventilation plate (14) of an outboard motor. The flushing device (12) uses a mounting bracket (22) to hold a resilient cup (20) compressed in place over the water inlet (18). A hose connector (24) allows the cup (20) to be connected to a water supply.

Abstract: An adaptor (27) is provided in the float bowl (11) of a carburetor (10) to force the secondary fuel passage (18) to draw fuel from the center of the float bowl (11). A cap (31) is provided at the top of the adaptor (27) to seal the top of the adaptor (27) while allowing the secondary metering rods (19) to extend through the adaptor (27).

Abstract: A flushing device (15) for supplying water to the cooling water inlets (14) of an outboard motor (10) uses a connecting pin (18) extending through the inlets (14) to attach a pair of sealing cups (16 and 17) over the inlets (14). A sliding spring latch (19) releasably attaches one of the cups (17) to the connecting pin (18). A hose connection (25) allows water to be supplied to the inlets (14) through the cup (16).

Abstract: A safety stop switch assembly (10) for controlling a device such as an outboard motor includes a toggle switch having a switch arm (12). A clip (16) is held in place around the switch arm (12) by a spring arm (21). The clip (16) can be attached to the operator by a lanyard (17). When the operator is sufficiently removed from the device, the lanyard (17) will pull the clip (16) away from the switch arm (12) and turn the switch off. The switch arm (12) can be used to control the outboard motor with or without the use of the clip (16).

Abstract: A control system (17) for cathodically protecting an outboard drive unit (11) from corrosion includes an anode (12) and a reference electrode (13) mounted on the drive unit (11). Current supplied to the anode is controlled by a transistor (20), which in turn is controlled by an amplifier (25). The amplifier is biased to maintain a relatively constant potential on the drive unit (11) when operated in either fresh or salt water.

Abstract: The engine (11) of a stern drive (10) is provided with a vacuum relief valve (28) to relieve any vacuum which may occur in the exhaust manifold (16), thus preventing water from entering the engine through the exhaust system. The relief valve (28) is connected to allow one-way flow from the intake manifold (15) to the exhaust system, thus providing an essentially closed system.

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 control linkage has levers for actuating the throttle lever of a carburetor and a primer pump. A slide actuator has cam grooves engaging ends of the levers to actuate the levers in response to movement of the slide actuator. An adjustable linkage is provided on the end of the lever to allow adjustment of the linkage without the use of tools. The adjustable link has an adjustment arm formed integrally with the lever and ratchet teeth on the arm and lever engage to allow adjustment.

Abstract: A valve (22) is provided in the exhaust system of a marine engine (11) which discharges its exhaust underwater. The valve (22) includes a valve member (23) formed of a stainless steel plate (24) and of silicon rubber (29). Holes (28) are provided in the plate (24) to form a mechanical bond with the silicon rubber molded to the plate (24).