Alternator Belt for Yanmar 2GM20F and 3GM30F Fresh-Water-Cooled Marine Engines – Replaces 25132-003700
Alternator Belt for Yanmar 2GM20F and 3GM30F Fresh-Water-Cooled Marine Engines – Replaces 25132-003700 is backordered and will ship as soon as it is back in stock.
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Alternator Belt for Yanmar 2GM20F and 3GM30F Fresh-Water-Cooled Mar...
Alternator Belt for Yanmar 2GM20F and 3GM30F Fresh-Water-Cooled Marine Engines – Replaces 25132-003700 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket alternator belt is listed for Yanmar 2GM20F and 3GM30F marine inboard engines equipped with fresh-water closed cooling systems. It is supplied as one individual replacement belt, not as a kit.
The belt is listed against the following Yanmar OEM reference numbers: 25132-003700, 123325-77360, 145613-77350, and 123325-77440. Confirm the number on your existing belt or engine parts documentation before ordering.
- Application: Alternator belt for fresh-water-cooled, closed-cooling configurations.
- Part type: Marine engine belt.
- Supply format: One replacement belt.
- Replacement use: Intended to replace the listed OEM-reference belt numbers when the engine application matches.
Part Number Matrix
These are the OEM reference numbers listed for this belt. Number listings do not replace confirmation of the complete engine application and cooling configuration.
| Brand | OEM Reference Number | Application Note |
|---|---|---|
| Yanmar | 25132-003700 | Alternator belt reference |
| Yanmar | 123325-77360 | Reference number listed for this belt |
| Yanmar | 145613-77350 | Reference number listed for this belt |
| Yanmar | 123325-77440 | Reference number listed for this belt |
Engine & Model Compatibility
The company application listing identifies this belt for the following Yanmar Marine Inboard models with fresh-water closed cooling. The listing does not specify a universal year range, serial-number range, shaft configuration, or horsepower range.
| Brand | Engine Model | Cooling Configuration | Function | OEM Reference Numbers |
|---|---|---|---|---|
| Yanmar Marine Inboard | 2GM20F | Fresh-water cooled, closed cooling | Alternator belt | 25132-003700; 123325-77360; 145613-77350; 123325-77440 |
| Yanmar Marine Inboard | 3GM30F | Fresh-water cooled, closed cooling | Alternator belt | 25132-003700; 123325-77360; 145613-77350; 123325-77440 |
Technical Specs
- Product Type
- Marine alternator belt
- Cooling-System Application
- Fresh-water cooled models with closed cooling
- Compatible Engine Models
- Yanmar 2GM20F and 3GM30F
- OEM Reference Numbers
- 25132-003700, 123325-77360, 145613-77350, 123325-77440
- Package Format
- Single belt
What’s in the Box
- 1 x Alternator belt
Installation Notes
- Turn the engine off, allow it to cool completely, and disconnect the battery.
- Confirm that the replacement belt matches the removed belt and the applicable OEM reference number.
- Loosen the alternator pivot and adjustment fasteners as required by the engine service procedure.
- Note the belt routing around the crankshaft, water-pump, and alternator pulleys before removing the old belt.
- Remove the old belt and inspect the pulley grooves for corrosion, damage, contamination, or unusual wear.
- Install the new belt in the original routing and ensure it is fully seated in each pulley groove.
- Adjust belt tension according to the engine manufacturer’s service specifications. Do not rely on a generic tension value when a model-specific specification is available.
- Tighten the adjustment and pivot fasteners to the applicable service-manual specifications.
- Reconnect the battery, start the engine, and verify that the belt tracks smoothly without abnormal noise or vibration.
- Stop the engine and recheck the belt installation and tension after the initial run-in period.
Maintenance & Troubleshooting
What are the signs of a worn alternator belt?
Common signs include squealing during startup or acceleration, visible cracking, fraying, glazing, belt dust, unusual vibration, or reduced alternator-charging performance. Inspect the pulleys as well as the belt when diagnosing a problem.
How should the belt be tensioned?
Use the tension procedure and deflection specification for your exact engine model. Excessive tension can damage bearings, while insufficient tension can cause slipping and poor charging.
Will this belt fit my Yanmar engine?
This listing is for Yanmar 2GM20F and 3GM30F engines with fresh-water closed cooling. Confirm the full model designation, cooling configuration, and one of the listed OEM reference numbers before ordering.
Does this listing include an alternator or installation hardware?
No. This listing includes one replacement alternator belt only. The alternator, fasteners, pulleys, and other engine components are not included.
When should the belt be replaced?
Inspect the belt during routine engine maintenance and replace it when cracking, fraying, glazing, contamination, abnormal noise, or other significant wear is present. Follow the engine manufacturer’s maintenance recommendations where available.
Safety & Important Information
- Verify the engine model, cooling configuration, belt routing, and OEM reference number before purchase.
- Do not work on a running engine. Disconnect the battery and allow hot components to cool before installation.
- Use the engine manufacturer’s service procedure for belt tension and fastener torque.
- This is an aftermarket replacement belt, not a Yanmar-branded OEM component.
- Professional installation is recommended if the correct belt routing or tension specification is uncertain.
About Sea Sierra
- Marine Parts Focus — Replacement components selected for marine engine service applications.
- Application Guidance — Check the complete model and cooling-system details before ordering.
- Replacement Value — Practical aftermarket parts for routine maintenance and repair.
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