Your Yanmar marine diesel engine is made to last, but will need regular maintenance to reach its full potential. After 50 hours of use, the fuel system must be inspected. Dirt and water may clog up the fuel system and cause unreliable start-ups. Over time, air will also accumulate in the fuel tank and degrade the quality of the fuel. When this occurs, the engine's power will be reduced. By removing water, debris and air from the fuel system, your Yanmar will be poised to perform at its best.
Turn off the engine and wait until it cools down sufficiently before continuing to the next step.
Drain water and dirt from the fuel tank. Place the pan under the drain plug, then pull open the drain plug.
Close the drain plug when the fuel runs clear. Safely dispose of the used fuel.
Drain water and dirt from the fuel filter. Place the pan under the drain plug, then rotate the plug screw to loosen it until the water and dirt start to stream out.
Tighten the plug screw, then check the fuel level. Add fuel up to 90 percent capacity.
Open the fuel plug on the fuel tank and then use a flat head screwdriver to rotate the air bleeding bolt two or three times.
Push the fuel priming pump knob and then release it. Continue to prime it until all the bubbles are removed and the fuel looks clear.
Tighten the air bleeding bolt and close the fuel plug.
