Thermostat Gasket – Fits Yanmar Marine Engines (Replaces 128400-49541)
Thermostat Gasket – Fits Yanmar Marine Engines (Replaces 128400-49541) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat Gasket – Fits Yanmar Marine Engines (Replaces 128400-49541)
Product Details
This Thermostat Gasket is a direct-fit replacement for various Yanmar marine diesel engines, including the 4JH, 4LH, 4LHA, 4LV, and 6LY series. It ensures a proper seal for the thermostat housing, which is critical for maintaining correct engine operating temperature.
It serves as a direct replacement for Yanmar part number 128400-49541.
- Direct replacement installation
- Designed for diesel fuel engines
- Built with OEM-spec construction for a precise fit
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yanmar | 128400-49541 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
The following table lists compatible Yanmar engine models. Verify your specific model for an exact match.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yanmar | 4JH(T)Z(TZ1,2)AY | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LH-(T,HT,DT,ST)E | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LH-HT/DTZ | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LH-UT,ST | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LH-UT/UTZAY/UTZ/ST/STZAY/STZ | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LHA-DT/HT E | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LHA-ST/DT/HT/(Z)E(P) | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH-HTBE | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH-TE | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH110 | 110 | 4-Stroke | 128400-49541 | ||
| Yanmar | 4JH2 | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH3-DTE | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH3-HTE | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH3-TE | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH3E | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH4-DTE | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH45 | 45 | 4-Stroke | 128400-49541 | ||
| Yanmar | 4JH4AE | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH4E | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH57 | 57 | 4-Stroke | 128400-49541 | ||
| Yanmar | 4JH5E | 4-Stroke | 128400-49541 | |||
| Yanmar | 4JH80 | 80 | 4-Stroke | 128400-49541 | ||
| Yanmar | 4LH-DTE | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LHA-DTP | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LHA-HTP | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LHA-STP | 4-Stroke | 128400-49541 | |||
| Yanmar | 4LV150 | 150 | 4-Stroke | 128400-49541 | ||
| Yanmar | 4LV195 | 195 | 4-Stroke | 128400-49541 | ||
| Yanmar | 4LV230 | 230 | 4-Stroke | 128400-49541 | ||
| Yanmar | 4LV250 | 250 | 4-Stroke | 128400-49541 | ||
| Yanmar | 4YB180 | 180 | 4-Stroke | 128400-49541 | ||
| Yanmar | 6AYAM-ET | 4-Stroke | 128400-49541 | |||
| Yanmar | 6BY2 | 4-Stroke | 128400-49541 | |||
| Yanmar | 6BY3 | 4-Stroke | 128400-49541 | |||
| Yanmar | 6LP | 4-Stroke | 128400-49541 | |||
| Yanmar | 6LPA-STP2 | 4-Stroke | 128400-49541 | |||
| Yanmar | 6LY2-STE | 4-Stroke | 128400-49541 | |||
| Yanmar | 6LY2A-STP | 4-Stroke | 128400-49541 | |||
| Yanmar | 6LY3-ETP | 4-Stroke | 128400-49541 | |||
| Yanmar | 6LY3-STP | 4-Stroke | 128400-49541 | |||
| Yanmar | 6LY3-UTP | 4-Stroke | 128400-49541 |
Technical Specs
- Product Type
- Thermostat Gasket
- Installation
- Direct replacement
- Fuel Type
- Diesel
- Dimensions
- 0.1" H x 6.5" W x 6.5" L
- Construction
- OEM-spec construction for precise fit
What’s in the Box
- 1 x Thermostat Gasket (128400-49541)
Installation Notes
- Ensure the engine is cool to the touch and disconnect the battery terminals for safety.
- Drain the engine coolant to a level below the thermostat housing.
- Locate and carefully unbolt the thermostat housing cover.
- Remove the old thermostat and gasket. Thoroughly clean both mating surfaces to remove any old gasket material or corrosion.
- Place the new thermostat into the housing, followed by the new gasket, ensuring correct alignment.
- Reinstall the housing cover and tighten the bolts to the manufacturer's specified torque in a crisscross pattern.
- Refill the cooling system with the appropriate coolant, reconnect the battery, and start the engine to check for any leaks.
Troubleshooting & FAQ
How do I know if my thermostat gasket needs replacing?
Signs of a failing gasket include coolant leaks around the thermostat housing, engine overheating, or fluctuating engine temperature readings. Visual inspection may reveal cracks or degradation of the gasket material.
Will this gasket fit engine models not listed?
This gasket is specifically designed for the Yanmar engine series listed. We cannot guarantee a proper seal or function on unlisted models. Always cross-reference the OEM part number 128400-49541 to ensure compatibility.
Is any sealant required with this gasket?
Generally, this type of gasket is designed to be installed dry on clean, flat surfaces. Applying sealant can sometimes interfere with a proper seal unless specified by your engine's service manual.
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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