916114-0845 Tohatsu BOLT

Illustration 1 g01087263
Lubrication system schematic (1) Upper rear idler bearing (2) Oil passage for the rear housing (3) Middle rear idler bearing (4) Rear oil line (5) Lower rear idler (6) Oil passage to rocker arms and camshaft bearings (7) Oil passage to the heads (8) Oil gallery in the head (9) Camshaft bearings (10) Shaft bearing for the live idler (11) Connecting rod with drilled oil passage (12) External oil line to rear gear train (13) Piston cooling jets (14) Lower front idler gear bearing (15) Main bearings (16) Right side turbocharger oil supply line (17) Left side turbocharger oil supply line (18) Auxiliary oil filter (if equipped) (19) Main oil gallery (20) Extension for the oil gallery (21) Oil filter bypass valve (22) Oil cooler bypass valve (23) Oil cooler (24) Oil pump (25) Oil pump bypass valve (26) Oil pan (27) Oil filterThe oil pump (24) is mounted to the bottom of the cylinder block within the oil pan (26) . The oil pump (24) pulls oil from the oil pan (26) . The oil then flows through a passage to the oil cooler (23) . Oil then flows through the oil filters (27) . The oil can flow into the main oil gallery (19) from the right side or the left side of the block. The location of the incoming oil supply is dependent on the location of the oil filters. The oil filters can be located on either side of the block. The oil then flows through a set of cross-drilled holes to the opposite side oil gallery.The main oil gallery (19) distributes oil to the following components: the crankshaft main bearings (15) , the piston cooling jets (13) , the extension of the oil gallery (20) , the turbocharger oil supply line (16) , the turbocharger oil supply line (17) and the live front idler gear bearings (10) . The main oil gallery (19) also distributes oil to the rear accessory drives through an external oil line (12) .Oil enters the crankshaft through holes in the bearing surfaces (journals) for the main bearing (15) . Passages connect the bearing surface (journal) for the main bearing (15) with the bearing surface (journal) for the connecting rod (11) . The oil flows upward through a drilled passage in the connecting rod to the piston pin bearing.The extension for the oil gallery (20) is located in the front right corner of the engine block. The extension for the oil gallery (20) supplies oil to the lower front idler gear bearing (14) .The oil flows to the live front idler gear bearing (10) and around bearing (10) to the oil passage for the cylinder head (7) . The oil then flows to the oil gallery in the cylinder head (8) . Then the oil flows to the oil passage (6) for the camshaft bearings (9) and the rocker arms.The oil for the lower rear idler bearing (5) is feed from a passage that is connected to the last rear main crankshaft bearing (15) . Oil is also fed from the rear main bearing to the rear oil line (4) . Then to the oil passage in the rear housing (2) for the middle rear idler gear bearing (3) and the upper rear idler gear bearing (1) .This oil circuit typically operates at a pressure of 214 kPa (31 psi) at low idle and at 400 kPa (58 psi) at rated speed.The oil pump bypass valve (25) limits the pressure of the oil that comes from the oil pump (24) . The oil pump (24) can put more oil into the system than oil that is needed. As the oil pressure increases, the oil pump bypass valve (25) will open. This allows the oil that is not needed to go back to the suction side of the oil pump (24) .Cold oil with high viscosity causes a restriction to the oil flow through the oil cooler (23) and the oil filter (27) . The oil cooler bypass valve (22) and the oil filter bypass valve (21) will open if the engine is cold. This will give immediate lubrication to all components. The oil pump (24) sends the cold oil through the bypass valves, around the oil cooler (23) , and the oil filter (27) , and to the main oil gallery (19) in the cylinder block.When the oil gets warm, the pressure difference in the bypass valves decreases. This closes the bypass valves. This creates a normal flow of oil through the oil cooler and through the oil filter.The bypass valves will also open when there is a restriction in the oil cooler (23) or a restriction in the oil filter (27) . This action lubricates the engine if the oil cooler (23) or the oil filter (27) are restricted. The bypass valve opening pressures vary with applications.An oil cooling chamber is formed by the forged lip at the top of the skirt of the piston and the cavity behind the ring grooves in the piston crown. Oil flow from piston cooling jet (13) enters the cooling chamber through a drilled passage in the skirt and returns to the oil pan (26) through the clearance gap between the crown and the skirt. The four holes that have been drilled from the piston oil ring groove to the interior of the piston drain excess oil from the oil ring.The oil breather allows blowby gases from the cylinders during engine operation to escape from the crankcase. The blowby gases discharge through the flywheel housing to a performed tube that is routed to the atmosphere. This prevents pressure from building up that could cause seals or gaskets to leak.Note: Engines that are equipped with an auxiliary oil filter (18) will pick up oil at a port. The filtered oil will be returned to the oil pan (26) .Oil Renewal System (If Equipped)
The purpose of the Oil Renewal System (ORS) is intended to increase the oil change interval. The purpose of