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How to Change the Oil and Filter on a Yanmar 3GM30F Diesel Engine

Over time your diesel engine oil will deteriorate and lose its lubrication and protection properties. This could lead to problems including wear and tear on moving parts, seizing of cylinders and premature engine failure. To prevent this it is recommended to change your engine oil at regular intervals.

Our engine is a Yanmar 3GM30, freshwater cooled engine, which has an oil capacity of 2.6 litres. Yanmar recommend that oil changes are carried out at 20 hours, then 30 hours, then every 100 hours after that.

Our last oil change was at 650 hours in May 2021, it is now February 2023 and we’re showing 772 hours, so a little over the 100 hours. It was time to do an oil change!

Here’s our step by step guide to how we carry out an oil and filter change on our Yanmar Marine Diesel engine.

First run the engine for a short period of time to warm it up and to allow the existing oil to get a little runnier; this will make it easier to extract. Allow the engine to cool for about 5 minutes and take a measurement of the current level, ideally this should be around 1/2 way when warm.

You will need a oil extractor to start pumping the oil out. We use a Seago Extract it 6Ltr Vacuum Oil Extractor Pump, inserting the thick end of the tubing into the container and screwing the pump onto the top. The thinner end of the tubing is inserted into the dipstick hole until it hits the bottom. Remove the oil filler cap on the top of the engine.

Start pumping! The oil should start to flow after a few pumps, once a vacuum has formed. If not, twiddle it about (very technical term there! 🤣) until this happens.

As you can see from the photo below we have extracted approximately 2.3 litres in this instance. Some will inevitably remain in the workings of the engine and some will be contained in the oil filter, which we will remove next. In the meantime replace the dipstick.

The position of the filter on this particular engine is a little troublesome; it is fitted sideways meaning as soon as you remove it expect to get messy! 😬 Using a strap wrench gently loosen the filter and remove. We recommend some old rags underneath and if you can, a bag wrapped around the old filter to try and catch as much of the oil as possible.

Clean the face where the filter mounts.

Smear a bit of new oil around the O ring on the new filter and pour a little oil into the new filter – not too much, remember this goes on sideways! We use a Yanmar Oil Filter 119305-35170, which cost us £10.49 from bottomlinemarine.com, but are available from most chandleries.

Screw the filter into place and nip it up (loving all these technical terms here 🤣) with the strap wrench. Do not over tighten.

Slowly refill oil to same quantity as removed. We use Yanmar Genuine Diesel Engine Oil SAE 15W- 40, again purchased from Bottomline Marine, at £10.67 per 1 litre bottle. These bottles also have a handy measuring gauge on the side so you can see how much you are using.

Once you have refilled, clean the filler cap and replace – don’t over tighten! Allow approximately 5-10 minutes for the oil to filter down and take a measurement; this will probably show more than you initially extracted, even if you put the same quantity back in, as it won’t have worked its way through and filled the oil filter yet. What you don’t want to see is a measurement of over full. If the measurement is looking a little low for your liking then top it up with a bit more oil. If it is too high then you will need to remove some by starting over again. Remember – easier to add than take away!

If the reading looks ok, run the engine for a short period of time and check for any obvious signs of leaks.

Switch off the engine and allow to cool before checking the levels once again. It should now be slightly lower than the last measurement as the oil should have pumped around the engine and into the filter. Ideally it should now be at a similar level to when you started the job.

And that’s it – you have successfully completed an oil change on a marine diesel engine 👏🏻

As always please proceed with caution. This is meant only as guidance and if you have any doubts please consult a marine engineer.

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