12706 Mercruiser SPACER, (.194 x .375)

The engine is cooled by forced circulation of coolant by the water pump.(1) Water Pump The water pump is driven by V-belt from the centrifugal pump installed on the front of the crankcase. A backward type impeller is press fitted at the rear shaft end of the water pump.A unit seal is installed between the impeller and water pump that prevents leakage of coolant. There is a drain hole provided at the bottom of the water pump case, which ensures that coolant, should it leak from the unit seal, does not enter bearings.One of the ball bearings is sealed and they are lubricated by grease packed in the water pump case. Grease can be supplied through the grease nipple.(2) Thermostat The thermostat is bottom bypass type.The thermostat pellet, of wax pellet type, contains a special wax which changes from a solid to liquid state and vice versa, depending on heat, and consequent change in its volume causes the valve to open or close, thereby changing the quantity of coolant which flows into the radiator and water pump (bypass side) to control the coolant temperature. A jiggle valve is provided in the air purge hole of the thermostat to quickly increase the coolant temperature.The jiggle valve is in down position by its own weight when the engine is stationary. When pouring in coolant, the air in the system is flown into the radiator through the clearance between the air purge hole and jiggle valve.When the engine is started, coolant circulates and the jiggle valve is forced upward by the hydraulic pressure. As a result, the valve closes the air purge hole, preventing outflow of coolant through the air purge hole.(3) Radiator The radiator, with a tube-and-corrugated-fin type core (and with a reserve tank on some models), not only cools the engine coolant but also separates vapor from liquid water and regulates pressure in the cooling system. The pressure cap regulates the pressure in the cooling system. When the pressure builds up in the system that exceeds a predetermined level, the pressure valve compresses the pressure spring, releasing the excessive pressure through the overflow pipe into the atmosphere.If equipped with a reserve tank, the coolant that has overflowed is channeled into it.When the coolant temperature drops and negative pressure builds up in the system, the vent valve opens to take in air to prevent the radiator from becoming deformed.If equipped with a reserve tank, coolant is taken from the reserve tank to prevent the radiator from becoming deformed and to keep the quantity of coolant in the system constant.If equipped with a pressure release lever on the cap, raising the lever upright opens the pressure valve and releases the pressure in the cooling system.2. Specifications
3. Service Standards
3.1 Service Standards Table
3.2 Tightening Torque Table
4. Special Tool
5. Service Procedure
5.1 Cooling Fan
Removal and installation
5.2 Water Pump
Removal and installation
Disassembly and inspection
Disassembly and Inspection Procedure (1) Remove the flange using the special tool, Gear Puller. (2) Remove the impeller using the special tool, Water Pump Impeller Puller. (3) Check the unit seals installed in the impeller and water pump case for damage and wear. If defects are evident, or when water leaks during operation, replace the unit seals with new ones. Whenever the unit seal is removed, it must be replaced with a new one. (4) Using a gear puller or press, remove the ball bearings. Do not remove the ball bearing except for replacement. (5) When the impeller and flange are removed from the water pump shaft, it may result in insufficient interference. If the interference is below the specification even reassembly is two times or less they must be replaced with new ones.Reassembly
5.3 Thermostat
Removal and installation
Do not remove the thermostat case and front hanger unless they cause water leak or other defects.Inspection
Agitate water in the container with the stirrer to obtain uniform temperature. For the inspection, use the following procedures. (1) Slowly heat water to the thermostat valve opening temperature. Keep this condition for about five minutes and make sure that the valve is open.(2) Raise the water temperature up to 90°C. Keep the condition for five minutes and measure the lift of pellet.(3) Lower temperature down to 65°C or below and ensure that the valve is fully closed. If the thermostat is found defective in any of the above items, replace it with a new one. Support the thermostat so that the heat source will not directly heat the thermostat.5.4 Radiator
Inspection (1) Using a copper wire or similar device, remove dirt, mud, and bugs from the front of radiator core with care to prevent damage to tubings. (2) Connect a hose to one of the radiator ports, cap the other port, and immerse the radiator into water. Using a radiator cap tester, force the compressed air under the specified inspection pressure from the hose end to check for leaks.If there is a leak, resolder the point of leakage or replace the radiator.(3) Inspection of Radiator Cap Check the spring tension and sealing condition of the pressure valve and vent valve. If defective, replace. Check the pressure valve opening pressure, using a radiator cap tester.5.5 Inspection and Adjustment of V-belt Tension
Adjust the belt tension to obtain the specified belt deflection when the center of each belt is pressed with a force of approximately 98 N (10 kgf). 1. A slack belt can be a cause of overheating and undercharge.2. An excessively tight belt may result in damaged bearings and belts.3. When paired belts are to be replaced, be sure to replace both.5.6 Cleaning of Cooling System
If the radiator is used for a long time, rust, scale, mud, etc. are deposited inside, resulting in overheat. Clean the cooling system with city water by using the following procedures.The city water to be used should have the following properties.Required properties of city water 1. Use a cleaning solution if the radiator is seriously obstructed or coolant is s