48747A 1 Mercury WATER PUMP BASE ASSEMBLY

Cylinder Block
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(1) Cylinder blockCylinder block (1) is made of cast iron. The six cylinders are arranged in-line.If a cylinder bore is damaged or if a cylinder bore is in excess of the service limit, a cylinder liner sleeve is available for repair.Cylinder Head
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Exploded view of the cylinder head (1) Valve guide (2) Cylinder head (3) Cylinder head gasket (4) Valve seat insert (5) Cap (6) Valve keepers (7) Valve spring retainer (8) Valve seal (9) Valve spring (10) ValveThe cast iron cylinder head (2) is fastened to the top of the cylinder block by twenty five bolts. A cylinder head gasket (3) is used between the engine block and the cylinder head in order to seal combustion gases, coolant, and oil. The inlet and exhaust ports are designed to improve air flow.The cylinder head assembly has two overhead valves (10) for each cylinder. Each valve is held in place by a single valve spring (9), a valve spring retainer (7), and two valve keepers (6). The cylinder head has steel valve seat inserts (4) for both the inlet and exhaust valves. The valves move in steel valve guides (1). Each valve guide is equipped with a synthetic rubber valve seal (8). The exhaust valve guides have a counterbore in order to prevent seizure of the valve stem that is caused by a buildup of carbon underneath the head of the valve. Both the valve seat inserts and the valve guides can be renewed.The overhead valves are operated by a rocker shaft assembly that is installed under a valve mechanism cover. The forged steel rocker arms are operated by cold drawn pushrods with hardened heads. The rocker shaft is supported by four steel brackets that support the rocker shaft between each pair of valves. The rocker shaft assembly and valve components are lubricated by an oil flow from the hollow rocker shaft. The rocker shaft receives a reduced oil flow from the oil feed of the camshaft.Valve lash is adjusted by adjustment screws and locknuts at the pushrod end of each rocker arm.The valve mechanism cover also contains an oil fill cap and breather pipe.Pistons and Connecting Rods
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Exploded view of the piston and connecting rod (1) Piston rings (2) Piston (3) Piston pin (4) Retaining rings (5) Piston pin bearing (6) Connecting rod (7) Connecting rod bearingPistons (2) have a combustion chamber in the top of the piston. The piston crater ensures an efficient mix of fuel and air.Piston rings (1) consist of two compression rings and an oil control ring. The groove in the piston for the top ring has a hard metal insert that reduces wear of the groove. The piston has a full skirt. The fully floating piston pin (3) is held in an axial location by retaining rings (4). The piston pin is placed off-center in order to reduce the noise level.Some engines are equipped with piston cooling jets. The piston cooling jets are located on the main webs of the cylinder block. The piston cooling jets spray lubricating oil onto the inner surface of the piston in order to cool the piston.The correct piston height is important in order to ensure that the piston does not contact the cylinder head and that the fuel has efficient combustion. The pistons and connecting rods (6) are matched to each cylinder.The connecting rod and the connecting rod cap are machined on the surfaces in order to provide a smooth mating surface. The cap is held in position by a pair of bolts with nuts.Crankshaft
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Exploded view of the crankshaft (1) Main bearings (2) Crankshaft (3) Crankshaft gear (4) Main bearing cap (5) Thrust washersCrankshaft (2) is forged from steel. The crankshaft has seven main bearing journals and six connecting rod bearing journals. The flywheel is attached to the large flange at the rear