31507 Mercury OIL SEAL, WATER PUMP BASE

Pistons and Connecting Rods
The pistons on 3013, 3014 and 3024 engines have a combustion chamber in the crown of the piston in order to provide an efficient mix of the fuel and the air. Due to the small size of the pistons on 3003 engines, the pistons have a flat crown.The piston pin is off-center in order to reduce the noise level.The pistons have two compression rings and an oil control ring.The correct piston height is important in order 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 in order to conform to requirements for emissions. The piston must not be machined in order to obtain the correct piston height.A piston and connecting rod are matched to each cylinder.One height of piston is available. The piston is marked "Std" on the crown. The underside of the piston is marked "SHIBAURA". This reference mark faces the right side of the engine. Refer to the Systems Operations, Testing and Adjusting Module, "Basic Engine" topic for procedures to measure the piston height.Identification marks on the connecting rod and the connecting rod cap must align. The identification marks face the right side of the engine.The main bearing caps have a chamfered edge on one side. The chamfer faces the front of the engine.Two main bearing caps have notches on the face of the cap that is opposite the side with the chamfer. The bearing cap with the notch toward the outside edge of bearing cap is the number 2 bearing on three cylinder engines. The bearing cap with the notch toward the outside edge of the bearing cap is the number 3 bearing on four cylinder engines.Timing Gear Case and Gears
The timing gear case contains the following components:
The front oil seal for the crankshaft pulley
The bearing for the crankshaft gear
The oil pump
The adjustment screw for setting the maximum fuel position
The adjustment screw for setting the maximum speed position
The mechanical stop control
The linkage for the fuel injection pump
Fuel control lever for the governor
The throttleThe crankshaft has a front bearing that is pressed in the cylinder block and three main journal bearings on three cylinder engines. The crankshaft has a front bearing that is pressed in the cylinder block and four main journal bearings on four cylinder engines. End play of the crankshaft on the 3003 engine is controlled by two thrust washers that are located on both sides of the bottom half of the rear main bearing.The 3013, 3014 and 3024 engines have three thrust washers. The thrust washers are hemispherical in shape. Two thrust washers are located on both sides of the bottom half of the rear main bearing. The third thrust washer is located on the rear side of the upper half of the main bearing.The crankshaft has front oil seals and rear oil seals.The timing case is made of aluminum. The timing gears are stamped with timing marks in order to ensure the correct assembly of the gears.The number one piston is at the top center position on the compression stroke when the following timing marks are aligned:
Idler gear
Crankshaft gear
Camshaft gear
Crankshaft pulley
Timing caseThe crankshaft gear turns the idler gear which then turns the camshaft gear.The idler gear contains the oil pump. The idler gear turns the gear for the tachometer.The crankshaft pulley drives the pulley on the water pump and the pulley which drives the alternator.