20884 Mercruiser WASHER

Illustration 1 g01108539
Lubrication System Schematic with a Warm Engine (1) Oil passage to front idler gear (2) Oil passage to fuel injection pump (3) Rocker arm shaft (4) Oil pressure connection (5) Oil manifold (6) Piston cooling jets (7) Camshaft bearing bore (8) Oil cooler bypass valve (9) Oil filter bypass valve (10) Engine oil cooler (11) Oil filter (12) Turbocharger (13) Oil pump (14) Oil pan (15) Oil supply line to turbochargerOil pump (13) pulls oil from oil pan (14). Then, oil pump (13) pushes the oil to engine oil cooler (10). From the oil cooler, the oil flows to oil filter (11). Next, the oil flows to oil manifold (5) and to turbocharger (12). From the oil manifold, oil flows to all main bearings and piston cooling jets (6). Oil passages in the crankshaft send oil to the connecting rod bearings. Oil from the front main bearing flows through oil passage (1) to the bearing for the fuel injection pump idler gear. Oil from the front main bearing also flows to camshaft bearing bore (7). The only bearing that receives pressure lubrication is the front camshaft bearing. Oil passage (2) from No. 4 main bearing sends oil to the fuel injection pump housing on the right side of the engine. The oil filter base feeds oil to the turbocharger through oil supply line (15). An oil passage from the rear of the cylinder block appears below the head bolt hole. The oil passage connects with a drilled passage that goes up next to the head bolt hole. A hollow dowel connects the vertical oil passage in the cylinder block to the oil passage in the cylinder head. The spacer plate has a hole with a counterbore on each side. The hollow dowel goes through this hole. An O-ring in each counterbore prevents the oil from any leaking around the hollow dowel. Oil flows through the hollow dowel and into a vertical passage. Then, the oil flows into the cylinder head and to the rocker arm shaft bracket. The rocker arm shaft has an orifice that restricts the oil flow to the rocker arms. The rear rocker arm bracket has an O-ring. The O-ring seals against the head bolt. This seal prevents the following occurrences:
Oil from reaching the head bolt
Any oil from leaking past the head gasket
Any oil from leaking past the spacer plate gasketThe O-ring must be replaced whenever the head bolt is removed from the rear rocker arm bracket.
Illustration 2 g01108574
Rocker Arm Oil Supply (A) Pressure OilHoles in the rocker arm shafts provide lubrication to the valve system components in the cylinder head. After the lubrication oil has worked, the lubrication oil flows back to the engine oil pan.There is a bypass valve in the oil pump. This bypass valve controls the pressure of the oil that is coming from the oil pump. The oil pump can send more oil into the system than the amount of oil that is needed. When there is more than enough oil, the oil pressure increases. The increased oil pressure opens the bypass valve. This allows the oil that is not needed to return to the engine oil pan.
Illustration 3 g01108577
Flow of Oil with Cold Engine (8) Oil cooler bypass (9) Oil filter bypass (10) Engine oil cooler (11) Oil filter (12) Turbocharger (13) Oil pump (14) Oil pan (15) Oil supply line to turbochargerBoth bypass valves (8) and (9) open under these conditions:
Cold engine
Cold starting conditionsThe bypass valves allow immediate lubrication to all components when cold oil with high viscosity causes a restriction to the oil flow through the following components:
Oil cooler (10)
Oil filter (11) Oil pump (13) sends the cold oil to oil manifold (5) in the cylinder block. The oil travels through the bypass valves. Then, the oil travels around both the oil cooler and the oil filter.When the oil becomes warm, the pressure difference in the bypass valves decreases, and the bypass valves close. Now, the oil flows normally through both the oil cooler and the oil filter.The bypass valves also open when there is a restriction in the oil cooler or in the oil filter. This action does not allow an oil cooler with a restriction to prevent lubrication of the engine. Furthermore, this action does not allow an oil filter with a restriction to prevent lubrication of the engine.