12754 Mercury SPRING

Take care to avoid mixing metric and inch fasteners. Mismatched or incorrect fasteners can result in mechanical damage or malfunction, or possible personal injury. Original fasteners removed during disassembly should be saved for assembly when possible. If new ones are required, caution must be taken to replace with one that is of same part number and grade.Metric thread fasteners are identified by material strength (grade) numbers on bolt heads and nuts. Numbers on bolts will be 8.8, 10.9, etc. Numbers on nuts will be 8, 10, etc.Engine Design
3116 Cylinder And Valve LocationBore ... 105.025 0.025 mm (4.1348 .0010 in)Stroke ... 127 mm (5.0 in)Displacement ... 6.6 liter (403 cu in)Number Of Cylinders ... 6Cylinder Arrangement ... in-lineValves Per Cylinder ... 2Valve Clearance Setting Intake ... 0.38 mm (.015 in)Exhaust ... 0.64 mm (.025 in)Type of Combustion ... Direct InjectionFiring Order ... 1-5-3-6-2-4Direction of Crankshaft Rotation (when seen from flywheel end) ... counterclockwise Front end of engine is opposite the flywheel end. Left side and right side of engine are as seen from flywheel end. No. 1 cylinder is the front cylinder.Fuel System
Fuel System Schematic
(1) Screen. (2) Inlet check valve. (3) Fuel transfer pump (integral with governor). (4) Outlet check valve. (5) Fuel filter. (6) Cylinder head. (7) Pressure regulating orifice. (8) Check Valve. (9) Primary fuel filter (if equipped). (10) Fuel tank. (A) Fuel priming pump (if equipped).Fuel from the fuel tank is pulled through an in-line screen (1) by fuel transfer pump (3). The fuel transfer pump is integral with the governor. Fuel is sent from the fuel transfer pump through fuel filter (5) and to a drilled passage in cylinder head (6). The drilled passage intersects a gallery around each unit injector to provide a continuous flow of fuel to all injectors. Unused fuel exits the cylinder head and passes through pressure regulating orifice (7) and check valve (8) before returning to fuel tank (10). Orifice (7) is located in the fuel return tube assembly. This pressure regulating orifice ensures adequate fuel gallery pressure for low idle fuel flows. Check valve (8) prevents bleed-off of fuel from the cylinder head during engine shutdown.When there is air on the inlet side of the fuel system, fuel priming pump (A) (if equipped) may be used to fill the fuel filter and fuel gallery (in the cylinder head), from the fuel tank before the engine is started. When the priming pump is used, check valves located in the fuel priming pump control the movement of fuel through the low pressure side of the system which removes air from the fuel lines and components back into the fuel tank.
Fuel Filter Lines Group
(3) Fuel transfer pump (integral with governor). (5) Fuel filter. (6) Cylinder head. (11) Fuel outlet port (to tank). (12) Fuel inlet port (to fuel transfer pump). (13) Fuel filter base. (14) Filtered fuel pressure tap. (15) Tube assembly (from fuel filter base to cylinder head fuel gallery in cylinder head). (16) Tube assembly (from transfer pump to fuel filter base).
Fuel Filter Lines Group (View A-A)
(1) Screen. (6) Cylinder head. (7) Pressure regulating orifice. (8) Check Valve. (11) Fuel outlet port (to tank). (12) Fuel inlet port (to fuel transfer pump). (16) Tube assembly (from transfer pump to fuel filter base). (17) Tube assembly (return to tank from fuel passage in cylinder head).Fuel Transfer Pump
Fuel Transfer Pump
(1) Screen. (2) Inlet check valve. (3) Spring. (4) Piston assembly. (5) Outlet check valve. (6) Piston check valve. (7) Tappet assembly. (8) Cam. (9) Passage.The fuel transfer pump is located in the front housing of the governor. The pump is activated by cam (8) attached to the shaft of the governor drive gear. Piston assembly (4) and tappet assembly (7) are stroked up and down by cam (8) and spring (3).Fuel enters the transfer pump through screen (1) and inlet check valve (2). On the upstroke of piston assembly (4), inlet check valve (2) closes. Outlet check valve (5) closes to prevent fuel from being pulled back in the pump from the outlet. As pressure increases above piston assembly (4), piston check valve (6) opens to allow fuel to fill passage (9).On the downstroke, increasing fuel pressure in passage (9) causes piston check valve (6) to close and outlet check valve (5) to open, pushing fuel to the main fuel filter and engine. Inlet check valve (2) opens to allow fuel to fill the cavity above piston assembly (4).During engine shutdown, the check valves are held closed by springs.Fuel Injector
Fuel Injection System
(1) Rocker arm. (2) Setscrew. (3) Follower. (4) Tappet spring. (5) Push rod. (6) Plunger. (7) Rack. (8) O-ring. (9) Barrel. (10) Fuel gallery. (11) Sleeve. (12) O-ring. (13) Lifter. (14) Cam.The fuel injection pump (unit injector) allows a small amount of fuel to be injected at the proper time into the combustion chamber. The fuel is supplied by fuel gallery (10) around each injector. Each of these galleries is connected by a drilled passage in the cylinder head. This passage provides a continuous flow of fuel to all unit injectors.The unit injector is isolated from the coolant passage by sleeve (11). This sleeve also provides the seating surface for the injector.Injection timing is determined by the angular location of cam (14) and the vertical location of plunger (6) in barrel (9). The angular location of the cam is controlled by the camshaft to crankshaft gear mesh at the front of the engine. The location of the plunger (fuel timing) is adjusted by setscrew (2).As the camshaft rotates, its profile is sent to rocker arm (1) by lifter (13) and push rod (5). The motion of rocker arm (1) is then sent to plunger (6) through follower (3).
Fuel Injector Pump (Unit Injector)
(4) Tappet spring. (6) Plunger. (7) Rack. (9) Barrel. (12) O-ring. (15) Gear. (16) Sleeve filter. (17) Helix. (18) Lower port. (19) Upper port. (20) Spring. (21) Check (needle valve).At the top of the plunger's stroke, fuel from fuel gallery (10) enters the injector around the edges