91962 Mercury NUT, TRANSOM BRACKET BOLT

Cylinder Block
Illustration 1 g00987345
Exploded view of the cylinder block (1) Cylinder block (2) Thrust washerCylinder block (1) is made of cast iron with an integral crankcase. The four cylinders are arranged in-line. The sides of the block extend below the centerline of the crankshaft in order to provide added strength. The cylinder block provides full support for the length of the cylinder bores. The cylinder sleeves are integral with the cylinder block.The journals of the camshaft run directly in the bores of the cylinder block. Thrust washer (2) is located at the rear of the block in order to control the end play of the crankshaft.Cylinder Head
Illustration 2 g00987347
Exploded view of the cylinder head (1) Valve mechanism cover (2) Rocker shaft assembly (3) Valve keepers (4) Valve spring retainer (5) Valve seal (6) Valve spring (7) Valve guide (8) Cylinder head (9) Cylinder head gasket (10) Valve seat insert (11) ValveThe cast iron cylinder head (8) is fastened to the top of the cylinder block by seventeen bolts. A cylinder head gasket (9) 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 (11) for each cylinder. Each valve is held in place by a single valve spring (6), a valve spring retainer (4), and two valve keepers (3). The cylinder head has steel valve seat inserts (10) for both the inlet and exhaust valves. The valves move in steel valve guides (7). Each valve guide is equipped with a synthetic rubber valve seal (5). 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 (2) that is installed under a valve mechanism cover (1). 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
Illustration 3 g00987348
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 skirt has a layer of graphite in order to improve the wear characteristics. 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 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
Illustration 4 g00987351
Exploded view of the crankshaft (1) Main bearings (2) Crankshaft (3) Crankshaft gear (4) Main bearing cap (5) Thrust washersCrankshaft (2) is forged from chrome molybdenum steel. The crankshaft has five main bearing journals and four connecting rod bearing journals. The flywheel is attached to the large flange at the rear of the crankshaft.End play of the crankshaft is controlled by three thrust washers (5). Two thrust washers are located on both sides of the rear main bearing. The third thrust washer is located on the rear face of the cylinder block (Illustration 1).Main bearings (1) have steel backs with an aluminum and tin bearing material. Main bearing caps (4) are made of cast iron.Crankshaft gear (3) is held on the tapered shaft of the crankshaft by a pair of woodruff keys. The crankshaft pulley is held in position by a nut on the front of the crankshaft.Camshaft
Illustration 5 g00994980
Exploded view of the camshaft (1) Thrust washer (2) CamshaftThe engine has a single camshaft (2) that is made of cast iron. The camshaft has four sets of lobes. Each set of lobes controls the movement of the inlet and exhaust valves for each cylinder.The camshaft is driven at the front end by the camshaft gear. As the camshaft rotates, the camshaft lobes move the valve system components. The valve system components move the cylinder valves.The camshaft gear must be timed to the crankshaft gear. The relationship between the lobes of the camshaft and the camshaft gear causes the valves in each cylinder to open at the correct time. The camshaft gear is held on the tapered shaft of the camshaft by a woodruff key.End play of the camshaft is controlled by thrust washer (1) that is mounted in front of the camshaft. The thrust washer is held in place by two bolts in the cylinder block.Timing Case and Gears
Illustration 6 g00987354
Exploded view of the timing case and gears (1) Camshaft gear (2) Fuel injection pump gear (3) Upper idler gear (4) Crankshaft front sealThe timing case is constructed of either aluminum or cast iron. The timing case cover contains cran