860171970 Mercruiser OWNER'S GUIDE

Illustration 1 g00930206
Flow diagram of the lubrication system
Pressure for the lubrication system is supplied by a gerotor oil pump. The crankshaft gear drives a lower idler gear. The lower idler gear drives the oil pump gear. The pump has an inner rotor and an outer rotor. The axis of rotation of the rotors are off-center relative to each other. There is an interference fit between the inner rotor and the drive shaft.The inner rotor has five lobes which mesh with the six lobes of the outer rotor. When the pump rotates, the distance increases between the lobes of the outer rotor and the lobes of the inner rotor in order to create suction. When the distance decreases between the lobes, pressure is created.Lubricating oil from the oil pan flows through a strainer and a pipe to the suction side of the engine oil pump. The lubricating oil flows from the outlet side of the pump through a pipe and a passage to the oil filter head. The oil then flows from the filter head through a pipe to a plate type oil cooler . The integral oil cooler is located on the left side of the cylinder block.From the oil cooler, the oil returns through a pipe to the oil filter head. The oil then flows from the filter head to the bypass valve and from the bypass valve to the oil filter.The oil flows from the oil filter through a passage that is drilled across the cylinder block to the oil gallery. The oil gallery is drilled through the total length of the left side of the cylinder block. If the oil filter is on the right side of the engine, the oil flows through a passage that is drilled across the cylinder block to the pressure gallery.Lubricating oil from the oil gallery flows through high pressure passages to the main bearings of the crankshaft. Then, the oil flows through the passages in the crankshaft to the connecting rod bearing journals. The pistons and the cylinder bores are lubricated by the splash of oil and the oil mist.Lubricating oil from the main bearings flows through passages in the cylinder block to the journals of the camshaft. Then, the oil flows from the front journal of the camshaft at a reduced pressure to the cylinder head. The oil then flows into the rocker arm shaft at a reduced pressure to the bearings of the rocker arm levers. The valve stems and the valve lifters are lubricated by the splash and the oil mist.The hub of the idler gear is lubricated by oil from the oil gallery. The timing gears are lubricated by the splash from the oil.Side mounted turbochargers are lubricated by oil from a connection on the right side of the cylinder block. An external line from the cylinder block supplies oil to the turbocharger. The oil then flows through a line to the oil pan.Top mounted turbochargers are fed from the oil filter head or from a connection on the right side of the cylinder block.This engine has piston cooling jets that are supplied with oil from the oil gallery. The piston cooling jets spray lubricating oil on the underside of the pistons in order to cool the pistons.