Alternator Belt – Fits Yanmar 1GM10 Marine Diesel Engine (Replaces 128170-77350)

Alternator Belt – Fits Yanmar 1GM10 Marine Diesel Engine (Replaces 128170-77350)

This high-quality aftermarket alternator and water pump belt is designed for Yanmar 1GM, 1GM10, 1GML, and 1GM10C marine diesel engines. It serves as a direct replacement for Yanmar part number 128170-77350 and other equivalent V-belts.

Important Fitment Note: Yanmar 1GM10 engines were produced with two different belt sizes. Early models typically use a 737mm belt, while later models (or those with an updated, larger alternator pulley) require a longer 788-790mm belt. Please measure your existing belt or check your engine's specific configuration to ensure you order the correct size.

• Drives both the engine alternator and raw water pump.
• Constructed from durable, fiber-reinforced rubber for longevity and reliable performance.
• Engineered to meet or exceed OEM specifications for fit and function.

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.

Alternative Belt Size for Later Models: The following models may use an alternative, slightly longer belt (OEM 105582-77790).

Technical Specifications

Package Contents

• 1 x Alternator Belt (Replaces Yanmar 128170-77350)

Installation Guide

1. Safety First: Ensure the engine is off and cool, and disconnect the battery's negative terminal.
2. Loosen the Alternator: Locate the alternator mounting bolts and pivot bolt. Loosen them just enough to allow the alternator to pivot.
3. Release Tension: Gently push the alternator towards the engine block to create slack in the old belt.
4. Remove Old Belt: Carefully slip the old belt off the crankshaft, water pump, and alternator pulleys.
5. Install New Belt: Route the new belt around the pulleys, ensuring it is seated correctly in the V-grooves.
6. Apply Tension: Pry the alternator away from the engine to apply tension to the new belt. Use a pry bar carefully to avoid damaging components.
7. Check Deflection: The belt is correctly tensioned when there is approximately 1 cm (½ inch) of deflection when pressed firmly with your thumb midway between pulleys.
8. Tighten Bolts: While maintaining tension, tighten the alternator's pivot and mounting bolts to the manufacturer's recommended torque.
9. Final Check: Reconnect the battery, start the engine, and check for any belt noise or slippage.

Troubleshooting & FAQ

Q: How do I know which belt size (737mm or 790mm) I need for my Yanmar 1GM10?
A: The best way to confirm is to measure your old belt's outer circumference. If that's not possible, consider your engine's age. Early models (pre-update, SN up to E03690) typically use the shorter 737mm belt. Later models or engines that have been retrofitted with a larger alternator pulley often require the longer 790mm belt.

Q: What are the signs my alternator belt needs replacing?
A: Common signs include loud squealing noises upon startup or acceleration, visible cracks, fraying, or glazing on the belt's surface, and excessive slack that cannot be corrected by tensioning the aternator.

Q: How do I check for correct belt tension?
A: When properly tensioned, the belt should have about 1 cm (½ inch) of "give" or deflection when you press down on it firmly with your thumb at the midway point between the alternator and crankshaft pulleys.

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.