884214 71 Mercury SCREW, (M6 x 16)

If the engine is to be stored in, or shipped to an area with below freezing temperatures, the cooling system must be either protected to the lowest outside temperature or drained completely to prevent damage.
Frequently check the specific gravity of the coolant for proper freeze protection or for anti-boil protection.
Clean the cooling system for the following reasons:
Contamination of the cooling system
Overheating of the engine
Foaming of the coolantNote: Air pockets can form in the cooling system if the cooling system is filled at a rate that is greater than 5 L (1.3 US gal) per minute.After you drain the cooling system and after you refill the cooling system, operate the engine. Operate the engine without the filler cap until the coolant reaches normal operating temperature and the coolant level stabilizes. Ensure that the coolant is maintained to the proper level.
Never operate an engine without water temperature regulators in the cooling system. Water temperature regulators help to maintain the engine coolant at the proper operating temperature. Cooling system problems can develop without water temperature regulators.
Refer to Special Instruction, SEBD0518, "Know Your Cooling System" and Special Instruction, SEBD0970, "Coolant and Your Engine" for more detailed information.Many engine failures are related to the cooling system. The following problems are related to cooling system failures: overheating, leakage of the water pump, plugged radiators or heat exchangers and pitting of the cylinder liners.These failures can be avoided with proper cooling system maintenance. Cooling system maintenance is as important as maintenance of the fuel system and the lubrication system. Quality of the coolant is as important as the quality of the fuel and the lubricating oil.Coolant is normally composed of three elements: water, additives and glycol.Water
Never use water alone without Supplemental Coolant Additives (SCA) or without inhibited coolant. Water alone is corrosive at engine operating temperatures. Water alone does not provide adequate protection against boiling or freezing.
Water is used in the cooling system in order to transfer heat.Distilled water or deionized water is recommended for use in engine cooling systems.DO NOT use the following types of water in cooling systems: hard water, softened water that has been conditioned with salt and sea water.If distilled water or deionized water is not available, use water with the properties that are listed in table 1.
Table 1
Caterpillar Minimum Acceptable Water Requirements
Property Maximum Limit ASTM Test
Chloride (Cl) 40 mL (1.4 oz) "D512", "D4327"
Sulfate (SO4) 100 mL (3.4 oz) "D516"
Total Hardness 170 mL (5.8 oz) "D1126"
Total Solids 340 mL (11.6 oz) "D1888"
Acidity pH of 5.5 to 9.0 "D1293" For a water analysis, consult one of the following sources:
Caterpillar dealer
Local water utility company
Agricultural agent
Independent laboratoryAdditives
Additives help to protect the metal surfaces of the cooling system. A lack of coolant additives or insufficient amounts of additives enable the following conditions to occur:
Corrosion
Formation of mineral deposits
Rust
Scale
Pitting and erosion from cavitation of the cylinder liner
Foaming of the coolantMany additives are depleted during engine operation. These additives must be replaced periodically. This can be done by adding Supplemental Coolant Additives (SCA) to Diesel Engine Antifreeze/Coolant (DEAC) or by adding ELC Extender to Extended Life Coolant (ELC).Additives must be added at the proper concentration. Overconcentration of additives can cause the inhibitors to drop out-of-solution. The deposits can enable the following problems to occur:
Formation of gel compounds
Reduction of heat transfer
Leakage of the water pump seal
Plugging of radiators, coolers, and small passagesGlycol
Glycol in the coolant helps to provide protection against the following conditions:
Boiling
Freezing
Cavitation of the water pump and the cylinder linerFor optimum performance, Caterpillar recommends a 1:1 mixture of a water/glycol solution.Note: Use a mixture that will provide protection against the lowest ambient temperature.Note: 100 percent pure glycol will freeze at a temperature of −23 °C (−9 °F).Most conventional heavy-duty coolant/antifreezes use ethylene glycol. Propylene glycol may also be used. In a 1:1 mixture with water, ethylene and propylene glycol provide similar protection against freezing and boiling. Refer to table 2 and table 3.
Table 2
Ethylene Glycol
Concentration Freeze Protection Boil Protection
50 Percent −36 °C (−33 °F) 106 °C (223 °F)
60 Percent −51 °C (−60 °F) 111 °C (232 °F)