0787025 EVINRUDE Service Manual

Illustration 1 g01085911
Cooling system schematic
(1) Cylinder head
(2) Expansion tank
(3) Return manifold
(4) Cylinder liners
(5) Temperature regulator housing
(6) Radiator
(7) Water pump
(8) Engine oil cooler The water pump is gear-driven. The water pump is located on the right hand side of the engine. The water pump supplies the coolant for the engine cooling system. The coolant is supplied to the following components:
Cylinder head (1)
Cylinder liners (4)
Engine oil cooler (8)
Air compressor (not shown)
Coolant conditioner element (not shown)
Illustration 2 g01121906
Right side view of engine
(3) Return manifold
(5) Temperature regulator housing
(7) Water pump
(8) Engine oil cooler Water pump (7) pulls the coolant from the bottom of radiator. The water pump is located on the right hand side of the front timing gear housing.The water pump impeller rotates at 1.37 times the engine speed. The water pump is driven by an idler gear. The idler gear is turned by the crankshaft gear. The water pump shaft is supported by two ball bearings. One ball bearing is located in the water pump housing. The other ball bearing is located in the front timing gear housing. The water pump impeller face is open. The impeller is made out of cast iron. The rear cover is an aluminum die casting. The water pump seal is a cartridge seal that is located on the inlet side of the water pump in order to provide good water flow around the seal for cooling. The coolant is pumped through engine oil cooler (9). The coolant then flows to the supply manifold. The supply manifold, which is located in the cylinder block, distributes coolant around the upper portion of the cylinder liners. At each cylinder, the coolant flows from the cylinder liner to the cylinder head. The cylinder head is divided into single cylinder cooling sections. In the cylinder head, the coolant flows across the center of the cylinder and across the injector seat boss. At the center of the cylinder, the coolant flows around the injector sleeve over the exhaust port. The coolant then exits into return manifold (3). The return manifold collects the coolant from each cylinder and the return manifold directs the flow to temperature regulator housing (5). When the coolant temperature regulator is in the closed position, the coolant flows through the coolant temperature regulator. This allows the coolant to flow directly back to the water pump for recirculation by bypassing the radiator. When the coolant temperature regulator is in the open position, the coolant is directed through the radiator and back to the water pump inlet.Supply Manifold
Cooling is provided for only the portion of the cylinder liner above the seal in the cylinder block. The coolant enters the cylinder block at each cylinder through slits in the supply manifold. The supply manifold is an integral casting in the cylinder block. The coolant flows around the circumference of the cylinder liner and into the cylinder head through a single drilled passage for each liner. The coolant flow is split at each cylinder liner so that 60 percent flows around the cylinder liner and the remainder flows directly to the cylinder head.Temperature Regulator Housing
Illustration 3 g01612076
Section view of the temperature regulator housing
(5) Temperature regulator housing
(9) Coolant temperature regulator The coolant temperature regulator is a full flow bypass type that is used to control the outlet temperature of the coolant. When the engine is cold, the coolant temperature regulator is in the closed position. This allows the coolant to flow through the coolant temperature regulator from the return manifold. This allows the coolant to bypass the radiator. The coolant goes directly to the water pump for recirculation. As the coolant temperature increases, the coolant temperature regulator begins to open directing some of the coolant to the radiator and bypassing the remainder to the water pump inlet. At the full operating temperature of the engine, the coolant temperature regulator moves to the open position. This allows all the coolant flow to be directed to the radiator. The coolant then goes to the water pump. This route provides the maximum heat release from the coolant. A vent line is recommended from the manifold to the radiator overflow tank in order to provide venting for the cooling system.Coolant for Air Compressor
Illustration 4 g01612094
(10) Outlet hose
(11) Inlet hose
(12) Air compressor The coolant that is used for air compressor (12) comes from the cylinder head through inlet hose (11). The coolant exits the air compressor through outlet hose (10) and flows back to the cylinder head.