Water Pump Drive Belt for Yanmar GM, HM & YM Series – Replaces 104511-78780 / 104511-78780E
Water Pump Drive Belt for Yanmar GM, HM & YM Series – Replaces 104511-78780 / 104511-78780E is backordered and will ship as soon as it is back in stock.
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Water Pump Drive Belt for Yanmar GM, HM & YM Series – Replaces ...
Water Pump Drive Belt for Yanmar GM, HM & YM Series – Replaces 104511-78780 / 104511-78780E is backordered and will ship as soon as it is back in stock.
Product Details
This replacement Water Pump Drive Belt for Yanmar GM, HM & YM Series is designed for the engine-driven water pump used on selected Yanmar marine inboard engines. It provides the belt drive needed to turn the water pump and support proper engine cooling when correctly installed and tensioned.
The belt is listed as a replacement for Yanmar part numbers 104511-78780 and 104511-78780E. Confirm your engine model and, where specified, the engine series number before ordering.
- Replacement belt for the engine-driven water pump.
- Fits selected Yanmar GM, HM and YM series applications listed below.
- Single belt supplied; this is not a kit.
Part Number Matrix
Use the following references to compare the belt with the part number shown for your engine.
| Brand | Part Number |
|---|---|
| Yanmar | 104511-78780 |
| Yanmar | 104511-78780E |
Engine & Model Compatibility
The company fitment information identifies this water pump belt for the following Yanmar marine engine models and variants. Model suffixes and regional versions are kept together below to help prevent an incorrect cross-application.
| Brand | Engine Series | Model or Variant | Notes |
|---|---|---|---|
| Yanmar | GM | 2GM, 2GMFL, 2GM20, 2GM20VE, 2GM20B, 2GM20C, 2GM20F | |
| Yanmar | GM | 2GM20-YEU, 2GM20C-YEU, 2GM20F-YEU, 2GM20FC-YEU | Regional variants |
| Yanmar | GM | 3GM, 3GMFLE, 3GM30-YEU, 3GM30C-YEU | |
| Yanmar | HM | 3HM, 3HMF | |
| Yanmar | YM | 2YM15 | |
| Yanmar | YM | 3YM20 | |
| Yanmar | YM | 3YM30 | Engine series number E01733 and after |
Technical Specs
- Product Type
- Water Pump Drive Belt
- Application
- Engine-driven water pump belt for selected Yanmar marine inboard engines
- Part Style
- Replacement belt
- Package Type
- Single belt, not a kit
- Reference Numbers
- Yanmar 104511-78780 and 104511-78780E
What’s in the Box
- 1 x Water Pump Drive Belt
Installation Notes
- Turn off the engine and allow it to cool completely before beginning work.
- Disconnect the battery or follow the isolation procedure specified in your engine service manual.
- Locate the water pump belt and loosen the applicable mounting or tensioning hardware.
- Remove the old belt from the pulleys and inspect the pulleys for damage, misalignment, looseness or contamination.
- Route the replacement belt around the correct pulleys according to the engine service manual.
- Set the belt tension according to the engine manufacturer's specification. Do not rely on a generic tension value when a model-specific specification is available.
- Tighten the mounting or tensioning hardware securely.
- Reconnect the battery, start the engine, and check that the belt runs smoothly without slipping, rubbing or unusual noise.
Troubleshooting & FAQ
How do I confirm this belt fits my Yanmar engine?
First, identify the complete engine model and compare it with the compatibility table. Then compare the part number on the existing belt or in your engine documentation with Yanmar 104511-78780 or 104511-78780E. For the 3YM30, also confirm that the engine series number is E01733 or later.
What are the signs of a worn water pump belt?
Inspect for cracking, fraying, glazing, chunking, excessive looseness or contamination by oil or coolant. Belt slip may produce noise and can reduce water pump speed, so investigate any abnormal belt sound or engine-temperature change promptly.
How often should the belt be replaced?
Inspect the belt during the maintenance interval specified for your engine and replace it if it shows wear, damage, contamination or loss of correct tension. Follow the engine manufacturer's service schedule for preventive replacement.
Can I install this belt on a model with a different suffix?
Do not assume that a similar-looking suffix has the same belt application. Confirm the complete model, regional variant and any applicable engine series-number condition against your engine documentation before installation.
Is this an OEM belt?
This listing is for a replacement belt referenced to Yanmar part numbers 104511-78780 and 104511-78780E. It is not represented as a genuine Yanmar-branded component.
Safety & Important Information
- Verify the complete engine model and applicable series-number condition before ordering.
- Install only with the engine stopped and cooled, following the engine service manual.
- Incorrect belt routing or tension can affect water pump operation and engine cooling.
- Do not use a damaged, contaminated or visibly mismatched belt.
About Sea Sierra
- Marine replacement parts selected for practical service and repair applications.
- Clear part-number and fitment information to help support accurate ordering.
- Parts supplied for maintenance and replacement of marine engine systems.
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