Alternator V-Belt – Fits Yanmar 2GM, 3GM Series Diesel Engines (Replaces 25112-003601)

Alternator V-Belt – Fits Yanmar 2GM & 3GM Series Diesel Engines (Replaces 25112-003601)

This high-quality aftermarket V-belt is designed for the alternator drive system on a range of Yanmar marine diesel engines, including the 2GM, 2GMF, 3GM, and 3GMF series. It serves as a reliable replacement for worn or damaged belts, ensuring proper alternator function and battery charging.

Engineered to meet or exceed OEM specifications, this belt provides a direct fit for several Yanmar part numbers, offering a durable and cost-effective maintenance solution.

• Installation Type: Direct replacement for a straightforward installation process.
• Material: Constructed from durable rubber to resist heat, oil, and abrasion.
• Function: Connects the engine crankshaft pulley to the alternator pulley to generate electrical power.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below.

Technical Specifications

Package Contents

• 1 x Alternator V-Belt (Replaces 25112-003601)

Installation Guide

1. Safety First: Ensure the engine is completely off and cool to the touch. Disconnect the battery's negative terminal to prevent accidental starting.
2. Locate the Belt: Identify the alternator and the old V-belt connecting it to the engine's crankshaft pulley.
3. Release Tension: Loosen the alternator's pivot bolt and the tensioning bolt on the adjustment bracket. This will allow the alternator to move and slacken the belt.
4. Remove Old Belt: Carefully slip the old belt off the alternator and crankshaft pulleys.
5. Verify the Part: Compare the new belt with the old one to ensure they are a match in length and width.
6. Install New Belt: Route the new V-belt around the crankshaft pulley first, then around the alternator pulley.
7. Apply Tension: Pry the alternator away from the engine to apply tension to the belt. A common rule is that the belt should have about 1/2 inch (13mm) of deflection when pressed firmly at its longest span.
8. Secure Bolts: While maintaining tension, tighten the alternator's tensioning bolt first, followed by the main pivot bolt.
9. Final Check: Reconnect the battery terminal. Start the engine and observe the belt to ensure it runs smoothly without slipping or squealing.

Troubleshooting & FAQ

How do I know if this V-belt will fit my Yanmar engine?
This V-belt is specifically designed for Yanmar 2GM, 2GMF, 3GM, and 3GMF series marine engines. To guarantee a perfect match, please verify that your old belt's part number is one of the following: 25112-003601, 25112-003600, or 121150-42290. You can also refer to the "Compatible Engine Models" table on this page.

What are the common signs of a failing alternator belt?
Key indicators include a high-pitched squealing noise from the engine bay, especially on startup or when under load. You may also see visible signs of wear like cracking, glazing (shiny surface), or fraying on the belt itself. A failing belt can also lead to a "battery" warning light on your dashboard due to improper charging.

How often should I inspect or replace my engine's V-belt?
Regular visual inspection during routine engine checks is highly recommended. There is no fixed replacement interval, but you should replace it immediately if you notice any signs of damage or wear. Proactively replacing the belt during major engine service can prevent unexpected failures at sea.

OEM vs. Aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.