12709 1 Mercruiser SEAL

Cylinder Block
Illustration 1 g06148238
Typical example
The cast iron cylinder block for the four cylinder engine has four cylinders which are arranged in-line. The cylinder block is made of cast iron. The cylinder block provides support for the full length of the cylinder bores. The cylinder bores are machined into the block.The cylinders are honed to a specially controlled finish to ensure long life and low oil consumption.The cylinder block has five main bearings which support the crankshaft. Thrust washers are installed on both sides of number 3 main bearing to control the end play of the crankshaft. The thrust washers can only be installed one way.Passages supply the lubrication for the crankshaft bearings. These passages are machined into the cylinder block.Cooling passages are cast into the cylinder block to allow the circulation of coolant.The camshaft journals run directly in the cylinder block.The engine has a cooling jet that is installed in the cylinder block for each cylinder. The piston cooling jet sprays lubricating oil onto the inner surface of the piston to cool the piston.A Multi-Layered Steel (MLS) cylinder head gasket is used between the engine block and the cylinder head to seal combustion gases, water, and oil.Cylinder Head
Illustration 2 g06162667
Typical example
(1) Valve keepers
(2) Valve spring retainer
(3) Valve springThe engine has a cast iron cylinder head (5). The inlet manifold is integral within the cylinder head. There are two inlet valves and two exhaust valves for each cylinder. Each pair of valves (6) are connected by a valve bridge that is controlled by a pushrod valve system.The ports for the inlet valves are on the right side of the cylinder head. The ports for the exhaust valves are on the left side of the cylinder head. The valve stems move in valve guides that are pressed into the cylinder head. There is a renewable stem seal (4) that fits over the top of the valve guide. The valve seats are replaceable.Pistons, Rings, and Connecting rods
Illustration 3 g06162684
Typical example
The pistons (9) have a Quiescent combustion chamber in the top of the piston to provide an efficient mix of fuel and air. The piston pin (8) is off-center to reduce the noise level. The position pin (8) is retained in the correct position by two circlips (3).The pistons have two compression rings (1) and an oil control ring (2). The groove for the top ring has a hard metal insert to reduce wear of the groove. The piston skirt has a low friction coating to reduce the risk of seizure when the engine is new.The correct piston height is important to ensure that the piston does not contact the cylinder head. The correct piston height also ensures the efficient combustion of fuel which is necessary to conform to requirements for emissions.The connecting rods (4) are machined from forged steel. The connecting rods have bearing caps (6) that are fracture split. Two connecting rod bearings (5) are installed between the connecting rod (4) and the bearing cap (6). The bearing caps on fracture split connecting rods are retained with Torx bolts (7). Connecting rods with bearing caps that are fracture split have the following characteristics:
The splitting produces an accurately matched surface on each side of the fracture for improved strength.
The correct connecting rod must be installed with the correct bearing cap. Each connecting rod and bearing cap have an unique serial number. When a connecting rod is assembled the serial numbers for the connecting rod and bearing cap must match.Crankshaft
Illustration 4 g06148343
Typical example
(1) Crankshaft
(2) Crankshaft thrust washers
(3) Crankshaft gearThe crankshaft is a spheroidal graphite iron casting.The crankshaft has five main journals. Thrust washers are installed on both sides of number 3 main bearing to control the end play of the crankshaft.The crankshaft changes the linear energy of the pistons and connecting rods into rotary torque to power external equipment.A gear at the rear of the crankshaft drives the timing gears. The crankshaft gear turns the idler gear and the camshaft gear. The camshaft gear turns the fuel injection pump gear. The idler gear turns the accessory drive gear (if equipped).A friction shim is installed onto the face of the crankshaft palm.Lip type seals are used on both the front of the crankshaft and the rear of the crankshaft.Gear Train
Illustration 5 g06148329
Typical example
The timing gears are made of steel.The crankshaft gear (3) drives the camshaft gear (2) and the idler gear (4). The camshaft gear (2) drives the fuel injection pump gear (1). The idler gear (4) drives the accessory drive gear (5) (if equipped).The camshaft rotates at half the engine speed. The fuel injection pump rotates at engine speed.Camshaft
The engine has a single camshaft. The camshaft is made of cast iron. The camshaft lobes are chill hardened.The camshaft is driven at the rear end. As the camshaft turns, 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 and the camshaft gear causes the valves in each cylinder to open at the correct time. The relationship between the lobes and the camshaft gear also causes the valves in each cylinder to close at the correct time.Front Housing
The crankshaft oil seal is mounted in the cover of the front housing. The front housing is made from aluminum.The engine oil pump is located in the front housing. The engine oil pump is driven from the front of the crankshaft.The water pump is on the front housing. The water pump pulley is driven by the front-end drive belt.