0318473 EVINRUDE COVER, Water passage

Fuel System
The engines can be equipped with a high-pressure gas fuel system or a low-pressure gas fuel system. Three different fuel systems are available:
Low Emission (LE) with high-pressure gas
LE with low-pressure gas
Standard (stoichiometric) with high-pressure gasThe LE engine with high-pressure gas requires a gas pressure within a range of 207 to 310 kPa (30 to 45 psi). The air/fuel ratio is adjusted so that there is excess oxygen in the engine exhaust. This excess oxygen reduces the NOx emissions.The LE engine with low-pressure gas requires a gas pressure within a range of 10 to 34 kPa (1.5 to 5 psi).The LE engines with NOx ratings of 2 grams have a nominal air/fuel ratio that results in approximately 8 percent of free oxygen in the exhaust. The LE engines are turbocharged and aftercooled.The Standard engines require gas pressure within a range of 138 to 172 kPa (20 to 25 psi). The nominal air/fuel ratio results in approximately 2 percent of free oxygen in the exhaust. The Standard engines are available with natural aspiration or turbocharged with aftercooling.The engines can be equipped with a dual fuel system in one of the following configurations:
A carburetor for high-pressure gas and a carburetor for low-pressure gas
Two parallel carburetors for low-pressure gasFor low-pressure gas engines, the carburetor is located between the air cleaner and the turbocharger. For high-pressure gas engines, the carburetor is located after the aftercooler and above the throttle. A governor and an actuator control the carburetor. The governor maintains the engine rpm. The two following types of carburetors are available:
Fixed venturi
Adjustable jetThe low-pressure gas engines can use either the fixed venturi or the adjustable jet. Standard engines and LE engines with high-pressure gas use the adjustable jet.The turbocharged aftercooled engines are equipped with flame arrestors. The flame arrestors are installed at the entrance of each inlet port. The flame arrestors prevent the engine backfire. The Engine backfire can occur in the following circumstances:
Malfunction of ignition
Engine shutdownThe flame arrestors will extinguish the flame before the flame can ignite in the inlet manifold.Ignition System
The engine is equipped with an Electronic Ignition System (EIS). The EIS provides dependable firing and low maintenance. The EIS provides precise control of the following factors:
Spark voltage
Spark duration
Ignition timingThe EIS also provides diagnostic capability that enhances troubleshooting. The primary ignition wiring is routed internally through the engine.The engines are equipped with protection from detonation (combustion knock). The detonation sensors are mounted on each side of the cylinder block. The ignition timing is delayed when excessive detonation is sensed. If detonation continues after full retardation, then the engine control module (ECM) shuts down the engine.Lubrication System
The engine lubrication oil is supplied by a pump that is driven by a gear. The oil is cooled and the oil is filtered. A bypass valve provides unrestricted flow of lubrication oil to the engine parts if the oil filter elements become plugged. The bypass valve will open if the oil filter differential pressure reaches 276 kPa (40 psi).Cooling System
The standard cooling system has a centrifugal pump that is driven by a gear. Four temperature regulators regulate the temperature of the coolant.The turbocharged engine has a Separate Circuit Aftercooler (SCAC). The aftercooler is required to operate at one of the following three temperatures. The temperature depends on the engine rating and the application.
32 °C (90 °F)
54 °C (129 °F)
70 °C (158 °F)Cogeneration uses energy from heat which would otherwise be wasted. In a cogeneration engine, the oil cooler is not in the jacket water circuit because the jacket water is too hot. The circuit for the oil cooler and the circuit for the aftercooler may be either a combined circuit or a separate circuit. In the combined system, the auxiliary pump circulates water through both the aftercooler and oil cooler cores. The combined system uses a thermostatic control to regulate the oil temperature. This thermostatic control prevents overcooling.Jacket water for cogeneration can be supplied at temperatures up to 127 °C (260 °F max). The customer must supply a pump for circulating the heated jacket water. The temperature of the jacket water is controlled by the customer.For engines that use landfill gas, the jacket water coolant temperature is maintained at approximately 110 °C (230 °F min). This temperature depends on the design of the cooling system and the ambient conditions. This temperature is required to prevent condensation of the water vapor that is in the fumes of the crankcase. Condensation of the water enables acids to form. Acids are more likely to form because landfill gas contains contaminants such as chlorides, fluorides, and halides. Acids will severely damage internal components to the engine.For engines that use landfill gas, the coolant that is supplied to the aftercooler is maintained at a temperature of 54 °C (129 °F). This temperature prevents condensation of moisture in the inlet air piping.Engine Service Life
Engine efficiency and maximum utilization of engine performance depend on adherence to proper operation and maintenance recommendations. These recommendations include the use of recommended lubricants, fuels, and coolants.For the engine maintenance that is required, refer to the Operation and Maintenance Manual, "Maintenance Interval Schedule" in the Maintenance Section.