Yanmar makes construction and agriculture products along with industrial and marine engines, generators and transmissions. Its diesel engines have a reputation for reliability. Regular maintenance and servicing will ensure that the engine will last several years. Always read the owner's manual and follow the proper use and care instructions. When servicing marine diesel engines keep water -- especially salt water -- from coming into contact with the engine. Salt is extremely corrosive.
Check the fuel and oil levels. If the engine fails to start, check to ensure the engine's oil and gas levels are sufficient. Check the spark plug. Damaged or worn spark plugs could cause the engine to fail to start. Check to ensure the fuel filter is full of fuel; if not, your engine may have a fuel starvation problem. Look for water in the fuel separator -- the filter closest to the fuel tank. A run-off valve below the tank can drain its contents.
Examine the tubes, linings and joints. A leak in one of the lines can easily cause problems such as the engine not starting. Check the injection pump. If the engine is sputtering or sporadic, the fuel injector may be malfunctioning. Check the lines to see whether the pump has become clogged.
Open the injector line at the cylinders. and crank the engine manually. Look for a loss of pressure or foamy substance, which indicates air in the fuel. Examine the engine housing for corrosion or knocks and dents.