Yanmar 4JH80 Water Pump Impeller Replacement
A worn impeller on your Yanmar 4JH80 starves the engine of cooling water and can overheat it in minutes. Below is the exact water-pump kit that fits this engine, a step-by-step video, and the parts you need to do the job yourself.
Check today’s price on Amazon →
Watch: how to replace it (step by step)
How to Replace Impeller – Yanmar 3H M35F
yanmar impeller change part 3
Tools Needed
- Hammer
- Screwdriver
Safety
- Be careful when using the hammer to avoid damaging surrounding areas.
- Ensure the area is well-ventilated when applying gasket maker.
Steps
- Remove the bottom bolts of the housing to separate it.
- Use a hammer to carefully tap the housing until it comes off.
- Be cautious while removing the housing, especially if there is teak nearby.
- Locate the housing for the water pump.
- Remove the cover of the water pump by unscrewing the four screws.
Tips
- If the housing is stuck, use a hammer to gently tap it until it comes off.
- Apply gray gasket maker around the housing to reseal it after reinstallation.
Which part do I need for my Yanmar 4JH80?
For most 4JH80 owners the part above (129670) 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 (2)
| Part number | Description | |
|---|---|---|
| YAN129670-42610 | IMPELLER KIT (Includes O-Ring) | Find on Amazon → |
| YANX0506590-01 | IMPELLER O-RING | 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 water pump impeller fits a Yanmar 4JH80?
The Yanmar 4JH80 uses the impeller sold as 129670, plus its OEM and aftermarket cross-references (2 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 impeller on a Yanmar 4JH80?
Replace the water pump impeller every 1-3 years or roughly every 200-300 running hours, whichever comes first — and sooner if you run in silty, sandy or shallow water.
What are the symptoms of a failing impeller on a Yanmar 4JH80?
A weak or missing telltale stream, engine temperature climbing above normal, or an overheat alarm are the classic warning signs. A worn impeller can overheat and damage the engine within minutes, so don't delay the job.
Do I need the full water pump kit or just the impeller?
For the 4JH80, fit the complete kit. The seals, O-rings, gasket and wear plate age alongside the impeller, and replacing them together is the reliable, do-it-once job.
How long does a water pump job take on a Yanmar 4JH80?
For a competent DIYer it's typically a 1-2 hour job of medium difficulty. The video above shows the job on a similar Yanmar diesel engine — the procedure matches, but check the 4JH80 manual for model-specific details.
Related guides
- Yanmar 3GM30F water pump / impeller
- Yanmar 2GM20F water pump / impeller
- Yanmar 3GM30 water pump / impeller
- Yanmar 2GM20 water pump / impeller
- All Yanmar water pump guides
- Free Yanmar boat valuation
As an Amazon Associate we earn from qualifying purchases — at no extra cost to you. Prices and availability are shown at checkout. This guide is for reference; always follow the engine manufacturer’s service manual.