Alternator V-Belt – Fits Yanmar 2YM15, 3YM20, 3YM30 Marine Diesels (Replaces 129612-42290E)

Alternator V-Belt – Fits Yanmar 2YM15, 3YM20, 3YM30 Marine Diesels (Replaces 129612-42290E)

This high-quality aftermarket alternator V-belt is designed for specific Yanmar YM series marine diesel engines. It is a direct-fit replacement for the OEM belt on Yanmar 2YM15, 3YM20, and 3YM30 engines produced after June 2004 up to serial number E20848. For engines with serial numbers E20848 and later, a flat serpentine belt (part number 128790-77580) is required instead.

This part replaces Yanmar OEM part number 129612-42290E, which supersedes the earlier belt version (119831-42290) used on engines manufactured before June 2004. Please verify your engine's model and serial number before ordering to ensure correct fitment.

• Direct Replacement Installation: Engineered to match OEM specifications for a direct fit without modification.
• Durable Construction: Made from robust rubber with internal fiber reinforcement for longevity and reliable performance.
• Broad Compatibility: Fits a range of popular Yanmar YM series engines within a specific production window.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers. This part is a direct replacement for the following OEM numbers.

Compatible Engine Models

Confirm your engine model/year in the table below.

Technical Specifications

Package Contents

1 x Alternator V-Belt (Replaces 129612-42290E)

Installation Guide

1. Safety First: Disconnect the vessel's battery terminals to prevent accidental starts.
2. Loosen Alternator: Locate and loosen the alternator's pivot bolt and adjusting bolt.
3. Create Slack: Gently push the alternator towards the engine block to create slack in the old belt.
4. Remove Old Belt: Carefully slip the old, worn belt off the crankshaft and alternator pulleys.
5. Install New Belt: Route the new belt around the pulleys, ensuring it is seated correctly in the grooves.
6. Apply Tension: Use a suitable lever to carefully pry the alternator away from the engine, tensioning the belt. Proper tension is typically about 1/2 inch (13mm) of deflection when pressed firmly at its longest span.
7. Secure Alternator: While maintaining tension, tighten the alternator adjusting bolt first, then securely tighten the pivot bolt.
8. Final Check: Re-verify the belt tension. Reconnect the battery terminals and start the engine to check for proper operation and listen for any unusual noises.

Troubleshooting & FAQ

Q: How do I know if this belt fits my Yanmar engine?

A: This V-belt is specifically for Yanmar 2YM15, 3YM20, and 3YM30 models built after June 2004 with an engine serial number before E20848. If your engine is older (pre-June 2004), you need part number 119831-42290. If your serial number is E20848 or higher, your engine uses a different flat serpentine belt (128790-77580).

Q: My old belt is marked "BANDO RPF 3375". Is this the correct replacement part?

A: Yes. "BANDO RPF 3375 13X925Li" is a common marking found on the original OEM Yanmar belts that this part is designed to replace. If your belt has this marking and your engine model matches our compatibility list, this is the correct replacement.

Q: What are the signs my alternator belt needs replacing?

A: Common symptoms of a failing belt include visible cracks, glazing, or fraying. You might also hear a high-pitched squealing sound from the engine, especially on startup, or notice that your battery is not charging effectively (indicated by a dimming of lights or a low voltage reading).

Q: OEM vs. Aftermarket?

A: 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.

Q: How fast do you ship and how much does it cost?

A: 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.

Q: What is your warranty and return policy?

A: 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.