Thermostat Cover Gasket – Fits Yanmar 3JH & 4JH Series (Replaces 129795-49551)
Thermostat Cover Gasket – Fits Yanmar 3JH & 4JH Series (Replaces 129795-49551) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat Cover Gasket – Fits Yanmar 3JH & 4JH Series (Replace...
Product Details
This aftermarket Thermostat Cover Gasket – Fits Yanmar 3JH & 4JH Series (Replaces 129795-49551) is engineered to create a reliable seal for the thermostat housing on a wide range of Yanmar marine and industrial diesel engines. It is compatible with 3JH and 4JH series engines, including popular models like the 3JH2, 3JH5E, 4JH, and 4JH4-HTE, covering a power range from 20 to 110 HP.
It serves as a direct replacement for Yanmar OEM part numbers 129795-49551 and its superseded predecessor, 129470-49550.
- Ensures a direct-fit installation for proper sealing.
- Constructed from high-temperature resistant gasket material for durability in marine diesel environments.
- Maintains proper sealing of the thermostat housing to prevent coolant leaks.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yanmar | 129795-49551 | Current OEM Part Number |
| Yanmar | 129470-49550 | Superseded by 129795-49551 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This part is known to fit a variety of Yanmar marine and industrial engines. Please check your specific model against the list below.
| Brand | Model | Rated HP | Stroke | OEM Part No. |
|---|---|---|---|---|
| Yanmar | 3JH2 | 38.7 | 4-Stroke | 129795-49551 |
| Yanmar | 3JH2(B)E | 38.7 | 4-Stroke | 129795-49551 |
| Yanmar | 3JH2T(B)E | 47.6 | 4-Stroke | 129795-49551 |
| Yanmar | 3JH25A | 20 | 4-Stroke | 129795-49551 |
| Yanmar | 3JH30A | 24 | 4-Stroke | 129795-49551 |
| Yanmar | 3JH3E | 40 | 4-Stroke | 129795-49551 |
| Yanmar | 3JH4E | 39 | 4-Stroke | 129795-49551 |
| Yanmar | 3JH5E | 39 | 4-Stroke | 129795-49551 |
| Yanmar | 3JH40-CR | 40 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH | 44 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH-TE | 55 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH-HTE | 66 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH-DTE | 77 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH2(B)E | 51 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH2T(B)E | 63.2 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH2HT(B)E | 76.1 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH2DT(B)E | 88.4 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH2UT(B)E | 100.6 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH3E EU | 56 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH3-TE | 75 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH3-HTE | 100 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH3-DTE | 125 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH4E | 54 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH4AE | 54 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH4-TE | 75 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH4-HTE | 110 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH5E | 54 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH45-CR | 45 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH57-CR | 57 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH80-CR | 80 | 4-Stroke | 129795-49551 |
| Yanmar | 4JH110-CR | 110 | 4-Stroke | 129795-49551 |
| Yanmar | 3TNE84 | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNE84 | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNE88 | 4-Stroke | 129795-49551 | |
| Yanmar | 3TNE88 | 4-Stroke | 129795-49551 | |
| Yanmar | 3TNV88-DMP | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNE84T | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDHQ | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDHQ(T) | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDSA | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDSA(T) | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDSAC | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDSA2 | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDSA2T | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDWI | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BDYE | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BNYE883 | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BNYE883T | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-BPHB | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-GNP | 4-Stroke | 129795-49551 | |
| Yanmar | 4TNV88-XMS | 4-Stroke | 129795-49551 |
Technical Specs
- Product Type
- Thermostat Cover Gasket
- Installation
- Direct fit
- Fuel Type
- Diesel
- Housing Material
- High-temperature resistant gasket material
- Function
- Maintains proper sealing of thermostat housing
- Weight
- 0.1 kg (0.22 lb)
- Dimensions
- 10.0 cm L x 7.0 cm W x 0.1 cm H
What’s in the Box
- 1 x Thermostat Cover Gasket (129795-49551)
Installation Notes
- Ensure the engine is completely cool and disconnect the battery.
- Drain the engine coolant to a level below the thermostat housing.
- Carefully remove the bolts securing the thermostat cover. Note their positions if they are different lengths.
- Remove the old gasket and thermostat. Clean both the housing and cover surfaces meticulously, removing all old gasket material and corrosion.
- Place the new gasket onto the housing, ensuring it aligns with the bolt holes.
- Re-install the thermostat cover and tighten the bolts in a crisscross pattern to the manufacturer's specified torque.
- Refill the cooling system with the appropriate coolant.
- Reconnect the battery, start the engine, and carefully check for any leaks around the housing as the engine warms up.
Troubleshooting & FAQ
How do I know if my thermostat gasket is failing?
Signs of a failing gasket include visible coolant leaks around the thermostat housing, engine overheating, or an unusually low coolant level. Look for crystallized coolant residue (typically green, pink, or orange) near the housing seam.
Is this gasket compatible with both raw water and freshwater cooled engines?
Yes, this gasket is made from high-temperature material suitable for both raw water (sea water) and freshwater/coolant-based systems found in the compatible Yanmar engine series.
What is the recommended replacement interval?
It is best practice to replace the thermostat cover gasket whenever the thermostat is replaced or the housing is removed for service. There is no fixed interval, but it should be inspected for leaks during routine engine checks.
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.
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