104511-78780E Water Pump V-Belt for Yanmar 2GM 2GM20 2GM20F 2GMF 2YM15 3GM 3GM30 3GM30F 3GMD 3GMDF 3GMF 3HM 3HM35 3HM35F 3HMF 3YM20 3YM30 YSM7 | JLM Marine

Water Pump V-Belt 104511-78780E – Fits Yanmar 2GM, 3GM, 3HM, 2YM, 3YM & YSM Series Marine Diesel Engines

This water pump V-Belt (104511-78780E) is engineered for Yanmar marine diesel engines, including the 2GM, 3GM, 3HM, 2YM, 3YM, and YSM series. Designed to drive the seawater pump reliably, this belt ensures proper cooling and optimal engine performance in demanding marine environments.

This belt directly replaces Yanmar OEM part numbers 104511-78780 and 104511-78780E, providing a cost-effective aftermarket solution without compromising on quality or durability.

• Fits Yanmar seawater pump assemblies across multiple engine families
• Designed for marine-grade durability and resistance to saltwater exposure
• Direct replacement for OEM belt – no modifications required

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 × Water Pump V-Belt (104511-78780E)

Installation Guide

1. Ensure the engine is completely shut down and cooled. Disconnect the battery to prevent accidental starting.
2. Locate the seawater pump on your Yanmar engine and identify the existing V-belt. Take note of the belt routing path around the pulleys.
3. Loosen the mounting bolts or adjustment mechanism on the seawater pump to create slack in the old belt. Remove the old belt carefully.
4. Inspect the pump pulley and crankshaft pulley for wear, cracks, or debris. Clean the pulley grooves if necessary.
5. Route the new V-belt around the pulleys following the original belt path. Ensure the belt is properly seated in all pulley grooves.
6. Adjust the pump position or tensioner to achieve the correct belt tension (typically allowing 1/2 inch deflection under moderate thumb pressure). Refer to your engine manual for specific tension specs.
7. Tighten all mounting bolts and adjustment hardware securely. Double-check that the belt is aligned and seated correctly.
8. Reconnect the battery and start the engine. Observe the belt for proper operation, alignment, and any unusual noise or vibration.
9. After the first few hours of operation, re-check belt tension and adjust if necessary. Belts may stretch slightly during initial break-in.

Troubleshooting & FAQ

Q: How do I confirm this belt fits my Yanmar engine?
A: Check the compatible engine models table above for your specific engine designation (e.g., 2GM20, 3HM35). You can also verify by cross-referencing the OEM part number 104511-78780 or 104511-78780E with your engine manual or existing belt.

Q: How often should I replace the water pump V-belt?
A: Inspect the belt every 100–200 operating hours or annually. Replace it if you notice cracking, fraying, glazing, or excessive wear. Many operators replace the belt every 2–3 years as preventive maintenance to avoid unexpected failures.

Q: What are the signs that my water pump belt is failing?
A: Common symptoms include squealing noises during operation, visible cracks or glazing on the belt surface, engine overheating due to reduced cooling pump efficiency, and belt slippage or loss of tension. Replace the belt immediately if any of these signs appear.

Q: Can I use this belt if my engine uses a different designation like M/19?
A: Yes, this belt is designated as M/19 and is the correct replacement for Yanmar engines specifying that belt size. Always verify against your engine's parts manual or existing belt marking.

Q: Is this an OEM belt or an aftermarket replacement?
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.