V-Belt – Fits Yanmar 2GM & 3GM Series (Replaces 25132-003100, 25132-003000, 128670-77350)
V-Belt – Fits Yanmar 2GM & 3GM Series (Replaces 25132-003100, 25132-003000, 128670-77350) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
V-Belt – Fits Yanmar 2GM & 3GM Series (Replaces 25132-003100, 2...
Product Details
This aftermarket Alternator V-Belt – Fits Yanmar 2GM & 3GM Series Diesel Engines (Replaces 25132-003100) is a direct replacement for Yanmar marine diesel engines in the 2GM and 3GM series, including models like 2GM20 and 3GM30. The V-belt connects the engine's crankshaft to the alternator pulley to generate electrical power.
It serves as a direct interchange for Yanmar OEM part numbers 25132-003100, 25132-003000, and 128670-77350.
- Connects the crankshaft to the alternator for power generation.
- Designed for engine-mounted installation between pulleys.
- Made from fiber-reinforced synthetic rubber for durability.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yanmar | 25132-003100 | Primary replacement part number. |
| Yanmar | 25132-003000 | Interchangeable older part number. |
| Yanmar | 128670-77350 | Alternative OEM part number. |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yanmar | 2GM20 | 18-20 HP | 4-Stroke | 1983–2005 | 25132-003100 | Serial numbers with "E" |
| Yanmar | 2GM20-YEU | 18-20 HP | 4-Stroke | 1997–present | 25132-003100 | |
| Yanmar | 3GM30 | 27-30 HP | 4-Stroke | 1983–2005 | 25132-003100/128670-77350 |
Technical Specs
- Product Type
- Alternator V-Belt
- Installation
- Engine-mounted between crankshaft and alternator pulleys
- Belt Type
- V-belt (single)
- Belt Profile
- A-31
- Housing Material
- Synthetic rubber with fiber reinforcement
- Housing Color
- Black
- Dimensions
- Length: 790 mm (31.1 in)
- Width
- 13 mm (0.51 in)
- Warranty
- 1 Year (aftermarket versions)
- OEM Fitment
- Verified Yanmar original equipment
What’s in the Box
- 1 x Alternator V-Belt (Replaces 25132-003100/25132-003000/128670-77350)
Installation Notes
- Ensure the engine is turned off and cooled completely.
- Disconnect the battery to prevent accidental starting.
- Loosen the alternator pivot bolt just enough to allow slight movement. Also loosen any adjuster-plate or tensioner bolts.
- Identify belt routing. Note the path around the crankshaft, water-pump, and alternator pulleys.
- Remove the old belt by swiveling the alternator or tensioner to relieve tension, then slip the belt off pulleys.
- Inspect pulley grooves for wear, rust, or corrosion. Clean them to bare metal if needed.
- Route the new belt following the same pulley path. Ensure it seats properly in all V-grooves.
- Tension the belt: A correctly tensioned V-belt deflects about 1 cm (½″) under moderate thumb pressure on the longest span.
- Tighten all bolts: Secure the adjuster-plate bolt, then the main pivot bolt to factory torque specs.
- Reconnect the battery.
- Start the engine and observe belt tracking to ensure it's centered in the grooves and running smoothly.
- Shut down and recheck tension after a short run. Re-tension if necessary as new belts may stretch slightly.
Troubleshooting & FAQ
How do I know if this belt fits my engine?
Check the Engine & Model Compatibility table to confirm your model is listed. This belt is a direct replacement for Yanmar part numbers 25132-003100, 25132-003000, and 128670-77350, primarily for 2GM and 3GM series engines.
What is the correct belt tension?
A correctly tensioned V-belt should deflect about 1 cm (½″) under moderate thumb pressure on the longest span between pulleys. Over-tightening can damage bearings, while a loose belt will squeal and fail to charge the battery properly.
What are the signs of a worn-out alternator belt?
Look for visible cracks, fraying, glazing, or missing chunks. Audible signs include persistent squealing from the engine bay. Poor electrical performance, such as dimming lights or a battery that won’t stay charged, can also indicate a slipping or broken belt.
How often should this V-belt be replaced?
We recommend inspecting the belt during regular engine maintenance. As a general rule, replace it every 3-5 years or earlier if you notice any signs of wear or damage. Always consult your engine's service manual for specific maintenance schedules.
Why are multiple OEM part numbers listed?
Yanmar used different part numbers (25132-003100, 25132-003000, 128670-77350) for these engines across various models and production years. This aftermarket belt is engineered to meet the specifications for all listed cross-references.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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