Yanmar 3YM30

This shows the parts of the Yanmar 3YM30 Diesel Saildrive motor.


The seawater pump contains an impeller which may need changing. The bearings may also need replacing.

The seawater pump contains an impeller. It must have water or it will be damaged. The coolant pump is centrifugal, and can run without water. It rarely breaks. When it does it is best to replace it.


The mixer is prone to corrosion and may need replacing, together with its gasket.


The sump is drained by sucking the oil out of the dipstick pipe.

If the primary fuel filter needs changing, air may get into the fuel line. If it does, loosen the bleeding screw on top of the secondary fuel filter and pump the manual lever on the fuel pump until clear fuel comes out of the bleeding screw (not frothy).

If the air in the fuel line occurs as a result of running out of fuel, it may also be necessary to loosen injectors 1 and 3 half a turn, before turning over the engine.

Loosening injector 1.

More instructions here, and here.

Injector pump

The start key drives a secondary solenoid.


If the engine does not start on the first attempt, turn off the raw water cock. When the engine starts, turn on the cock immediately. Prolonged cranking with the raw water turned on will fill the engine cylinders with water!

See more at the Yanmar Help Site. Also discussion on Cruisers Forum.

The engine mounts need to be tight.

The three anodes should be checked when the boat is slipped, and the sail-drive oil changed..






Yanmar Help FAQs