Yanmar 2GM20 Anode Replacement
Sacrificial anodes are the cheap parts that protect the expensive metal on your Yanmar 2GM20 from galvanic corrosion. Below is the anode we recommend, which 2GM20 variants it fits, a step-by-step video, and answers to the zinc-vs-aluminium question.
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Watch: how to do it (step by step)
How to replace the anode on a Yanmar 2GM20
Winterising Yanmar 2GM20-YEU #antifreeze #thermostat #anode #waterpump #zinc #drain valve
Tools Needed
- 24mm socket
- Long wrench handle
- Gasket maker
- Kitchen towel
Safety
- Ensure the engine is cool before starting any work.
- Wear gloves to protect your hands from any residual antifreeze or engine oil.
Steps
- Locate the drain valve on the starboard side of the engine, typically forward of the lift pump and above the oil dipstick.
- Remove the plastic cap from the drain valve.
- If no fluid comes out, remove the anode using a 24mm socket and a long wrench handle.
- Drain the block by removing the anode.
- Remove the thermostat, which is found near the drain valve.
- Drain the hoses and fill the head with a mixture of antifreeze and water.
- Renew the thermostat with a new one specified to 42°C.
- Open the water pump to drain any remaining water.
- Slacken off the belt and remove the water pump.
- Drain the water pump and ensure no water remains.
- Create a funnel to fill the block via the thermostat hole with a 50% mixture of ethylene glycol and water.
- Fill the block with the antifreeze mixture.
Tips
- If the drain valve is clogged, removing the anode will help drain the block.
- Ensure you have enough antifreeze mixture prepared, as you may not need all of it.
- Test the old thermostat at home to check its condition.
Which part do I need for my Yanmar 2GM20?
For most 2GM20 owners the part above (YAN23414-250000) is the right choice. Price tip: the aftermarket numbers are usually noticeably cheaper than the OEM-branded box — it is the same physical part. If you need an exact match, these compatible part numbers also fit:
Show all compatible part numbers (1)
| Part number | Description | Fits | |
|---|---|---|---|
| YAN27210-200300 | Yanmar Zinc | 2GM20 | Find on Amazon → |
Many of these are the same physical part under different brand numbers. Build years are shown where our parts data has them. Where a variant has no years, only the model code is listed. Confirm against your engine plate before ordering.
Frequently asked questions
What anode fits a Yanmar 2GM20?
The Yanmar 2GM20 uses the anode sold as 23414-250000, plus its OEM and aftermarket cross-references (1 compatible numbers are listed above). Confirm the number against your engine's model code and year plate before ordering.
How often should I replace the anode on a Yanmar 2GM20?
Inspect your anodes at least once a season and replace them once they are about half eaten away.
Zinc, aluminium or magnesium anodes?
Zinc and aluminium anodes are for saltwater (aluminium also works in brackish water); magnesium is for freshwater only. Pick one type and use it consistently across the engine — mixing types reduces protection.
What happens if the anodes on a Yanmar 2GM20 wear out?
Galvanic corrosion starts attacking the propeller, gearcase and trim hardware instead — repairs that cost far more than a set of anodes. Anodes are consumables; replacing them on time is the whole point.
How long does an anode change take on a Yanmar 2GM20?
Typically well under an hour with basic hand tools — one of the easiest DIY jobs on the engine. The video above shows where each anode sits.
Related guides
- Yanmar 1GM10 anode
- Yanmar 2QM15 anode
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