812561A 2 Mercruiser DRIVESHAFT ASSEMBLY

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. No. 2 diesel fuel is the most commonly used fuel. No. 1 diesel fuel, or a blend of No. 1 and No. 2, is best suited for cold weather operation.Quantities of No. 1 diesel fuel are limited, and generally only available during the winter months in the colder climates. During cold weather operation, if No. 1 fuel is unavailable, it may be necessary to use No. 2 diesel fuel.There are three major differences between No. 1 and No. 2 diesel fuel. No. 1 diesel fuel has: * a lower cloud point* a lower pour point* 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. You should not experience any other operating effects.The cloud point is the temperature at which a cloud or haze of wax crystals begins to form in the fuel and cause fuel filters to plug. The pour point is the temperature which diesel fuel begins to thicken and be more resistant to flow through fuel pumps and lines.Be aware of these fuel values when purchasing your diesel fuel. 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.Before troubleshooting for low power or poor performance in winter months, check the type of fuel being used.When No. 2 diesel fuel is used: starting aids, engine oil pan heaters, engine coolant heaters, fuel heaters, and fuel line insulation also provide a means of minimizing starting and fuel problems in cold weather.Fuel Related Components in Cold Weather
Fuel Tanks
Condensation can form in partially filled fuel tanks. Top off fuel tanks before leaving overnight.Fuel tanks should contain some provision for draining water and sediment from the bottom of the tanks. Some fuel tanks use supply pipes that allow water and sediment to settle below the end of the fuel supply pipe.Some fuel tanks use supply lines that take fuel directly from the bottom of the tank. If equipped with this system, regular maintenance of the fuel system filter(s) is important.Check the fuel level in the day tank daily by observing the sight gauge. Drain the water and sediment from any fuel storage tank weekly, at the oil change period, and before the fuel tank is refilled. This will help prevent water and/or sediment from being pumped from the fuel storage tank into the engine fuel tank.Fuel Filters
A primary fuel filter is installed between the fuel tank and the engine fuel inlet. After changing the fuel filter(s), always prime the fuel system (if equipped with a priming pump) to remove air bubbles from the system.The micron rating and location of a primary fuel filter is important in cold weather operation. The primary filter and the fuel supply line to the primary filter 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. Refer to the Parts Manual for this engine to determine that part numbers required for the primary fuel filter.Fuel Heaters
Fuel heaters prevent fuel filters from plugging in cold weather due to waxing. A fuel heater should be installed so that the fuel is heated before it enters the first (primary) fuel filter.Select a fuel heater that is mechanically simple, yet adequate for the application. The fuel heater should also prevent overheating of the fuel. High fuel temperatures reduce engine performance and power availability. 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. Only thermostatically controlled or self-regulating fuel heaters should be used with this engine. Non-thermostatically controlled fuel heaters can heat the fuel in excess of 65°C (149°F). A loss of engine power can occur if the fuel spply temperature exceeds 37°C (100°F). 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 Caterpillar part no. 7C3557Hot Joint Caterpillar part no. 7C3558For further information on fuel heaters, contact your Caterpillar dealer.