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 exact anode that 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 Anode – 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 | |
|---|---|---|
| YAN27210-200300 | Yanmar Zinc | Find on Amazon → |
Many of these are the same physical part under different brand numbers. Confirm against your engine plate before ordering.
Frequently asked questions
What anode fits a Yanmar 2GM20?
The Yanmar 2GM20 uses the anode sold as YAN23414-250000, 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
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