V-Belt – Fits Yanmar 4LH & 4LHA Series Marine Engines (Replaces 121850-42280E, 121850-42280)
V-Belt – Fits Yanmar 4LH & 4LHA Series Marine Engines (Replaces 121850-42280E, 121850-42280) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
V-Belt – Fits Yanmar 4LH & 4LHA Series Marine Engines (Replaces...
Product Details
This high-quality V-Belt for Yanmar 4LH & 4LHA series marine engines is an essential component for driving the alternator and fresh water pump. It is designed for reliable performance in fresh-water cooled inboard diesel engines, ensuring your charging and cooling systems function correctly.
This belt is a direct replacement for Yanmar part numbers 121850-42280E and 121850-42280, and is also an interchange for MITSUBOSHI RECMF-6460.
- Installs as the primary alternator drive belt.
- Engineered for fresh water pump drive applications.
- Made from durable, fiber-reinforced rubber to ensure longevity.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yanmar | 121850-42280E | Current OEM Part Number |
| Yanmar | 121850-42280 | Superseded by 121850-42280E |
| MITSUBOSHI | RECMF-6460 | Aftermarket cross-reference |
Engine & Model Compatibility
Confirm your engine model in the table below to ensure accurate fitment.
| Brand | Model | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|
| Yanmar | 4LHA-DTE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-DTP | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-DTZE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-DTZP | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-HTE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-HTP | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-HTZE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-HTZP | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-STE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-STP | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-STZE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LHA-STZP | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-DTE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-DTZ | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-HT | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-HTE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-HTZ | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-HTZAY | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-ST | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-STE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-STZ | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-STZAY | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-TE | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-UT | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-UTZ | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-UTZAY | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-WST | 4-Stroke | 121850-42280E | |
| Yanmar | 4LH-WSTZY | 4-Stroke | 121850-42280E | |
| Yanmar | 4TN100TE-GB1 | 4-Stroke | 121850-42280E | Industrial application |
| Yanmar | 4TN100TE-G1 | 4-Stroke | 121850-42280E | Industrial application |
Technical Specs
- Product Type
- V-Belt
- Installation
- Alternator drive belt
- Material
- Rubber with fiber reinforcement
- Application
- Fresh water pump drive
- Color
- Black
- Weight
- Approximately 0.4 kg (0.88 lb)
- Tension Specification
- Deflects approximately 1 cm (½″) under moderate thumb pressure on the longest span
- Warranty
- 1-year against manufacturing defects (aftermarket); 6-month (OEM)
- Other Technical Attributes
- Often printed with "MITSUBOSHI - RECMF-6460" on the belt
What’s in the Box
- 1 x V-Belt (Replaces 121850-42280E / 121850-42280)
Installation Notes
- Ensure the engine is turned off and cooled completely.
- Disconnect the battery to prevent accidental starting.
- Loosen the alternator pivot bolt and any adjuster bolts enough to allow movement.
- Note the routing of the old belt around all pulleys before removal.
- Relieve tension by moving the alternator, then slip the old belt off the pulleys.
- Inspect pulley grooves for wear or debris and clean them if necessary.
- Route the new belt, making sure it is properly seated in all V-grooves.
- Tension the belt by swiveling the alternator away from the engine. A correctly tensioned belt deflects about 1 cm (½″) under moderate thumb pressure on its longest span.
- Tighten the adjuster-plate bolt first, then the main pivot bolt to factory torque specifications.
- Reconnect the battery.
- Start the engine and briefly observe the belt to ensure it runs smoothly and is centered in the grooves.
- Shut down the engine and recheck tension, as new belts can stretch slightly after the initial run.
Troubleshooting & FAQ
How do I know if this V-belt fits my engine?
This belt is designed for Yanmar's 4LH and 4LHA series marine diesel engines. To guarantee a match, please find your specific engine model in the "Engine & Model Compatibility" table on this page before ordering.
What are the signs of a failing V-belt?
Common indicators include loud squealing noises (especially during startup or when cold), visible cracks, glazing (a shiny, smooth surface), fraying, or issues with your battery charging system due to a slipping alternator.
How tight should I make the new belt?
A correctly tensioned v-belt should deflect about 1 cm (or ½ inch) when you apply moderate thumb pressure to the middle of its longest span. Over-tightening can damage bearings, while a loose belt will slip and wear out quickly.
When should this V-belt be replaced?
There is no universal replacement interval, as life depends on engine hours and conditions. We recommend inspecting the belt at every routine engine service. Replace it proactively if it shows any signs of wear like cracks, fraying, or glazing to prevent unexpected failure at sea.
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.
Payment & Security
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