881646 Mercruiser SCREW, (M6 x 20)

Fuel And The Effect From Cold Weather
The two types of diesel fuel available for your engine are typically grades No. 1 and No. 2. Although No. 2 diesel fuel is the most commonly used fuel, No. 1 diesel fuel is the fuel that is best suited for cold weather operation.During cold weather operation, it may be necessary for you to use No. 2 diesel fuel since quantities of No. 1 diesel fuel are limited and generally are only available during the winter months and in the colder climates.There are two major differences between No. 1 and No. 2 diesel fuel. No. 1 diesel fuel has a lower cloud point and a lower pour point.The cloud point is the temperature at which a cloud or haze of wax crystals will begin to form in the fuel and cause fuel filters to plug. The pour point is the temperature which diesel fuel will begin to thicken and be more resistant to flow through fuel pumps and lines.Be aware of these fuel values when purchasing your diesel fuel and anticipate the average outside (ambient) temperature for the area your engine will be operating. Engines fueled in one climate may not operate satisfactorily if moved to another because of problems that result from cold weather. The average No. 1 diesel fuel has a lower Btu (kj) (heat content) rating per unit volume of fuel than the average No. 2 diesel fuel. When using No. 1 diesel fuel, you may notice a drop in power and fuel efficiency, but should not experience any other operating effects.Before troubleshooting for low power or poor performance in winter months, check the type of fuel being used.The use of starting aids, engine oil pan (crankcase) heaters, engine coolant heaters, fuel heaters and fuel line insulation also provide a means of minimizing starting and fuel problems in cold weather when No. 2 diesel fuel is used.Fuel Related Components In Cold Weather
Fuel Heaters
Fuel heaters prevent plugging of the fuel filters in cold weather due to waxing. Non-thermostatically controlled fuel heaters can heat the fuel in excess of 150°F (65°C). High fuel temperatures reduce engine performance and reliability.A fuel heater should be installed so that the fuel is heated before it enters the first (primary) fuel filter.Use a fuel heater that is mechanically simple, yet adequate for the application. The fuel heater should also prevent overheating of the fuel. Choose a fuel heater with as large a heating surface as practical. Small heaters can be too hot in their limited surface area.Disconnect or deactivate the fuel heater in warm weather. A loss of engine power can occur if the fuel supply temperature exceeds 85°F (30°C). Heat exchanger-type fuel heaters should have a bypass provision to prevent overheating of the fuel in warm weather operation.The following fuel heaters are recommended for use with Caterpillar engines.Thermoblend Cat part no. 7C3557Hot Joint Cat part no. 7C3558For further information on fuel heaters, contact your Caterpillar dealer.Fuel Filters
The use of an auxiliary primary fuel filter and/or water separator is recommended between the fuel tank and the engine mounted fuel filter. The micron rating and location of a primary fuel filter is important in cold weather operation. The primary fuel filter and its fuel supply line are the most common components affected by cold fuel.The micron rating of the primary fuel filter should only be fine (low) enough to protect the fuel transfer pump. A very fine (low micron rating) primary filter, can be more easily plugged by wax in cold weather. A primary filter, with a micron rating as fine as a secondary filter, can cause waxing problems. A 9M2341 Filter element is recommended as a cold weather primary fuel filter.The best location for the primary fuel filter is in the engine compartment, where it will benefit from the radiant heat of the engine. A filter mounted outside the frame rails, or any location exposed to wind, can be a persistent problem in cold weather.Maintain Engine Compartment Temperature
Radiator shutters and on/off fans are excellent devices for maintaining engine area/compartment temperatures. The radiator shutter thermostat should open the shutters at a temperature that is 10°F (6°C) higher than the opening temperature of the engine thermostat.On/off fan thermostats should open at a temperature that is 5° to 10°F (3° to 6°C) higher than the temperature setting of the shutters. The sequence of these events is important to maintain engine temperature and obtain optimum fuel economy.If shutters are not used, fan temperature operation is typically 10° to 15°F (6° to 9°C) above the thermostat temperature.