Gasket, Cover – Fits Yanmar 3JH25A/3JH30A Marine Engines (Replaces 129100-01621)
Gasket, Cover – Fits Yanmar 3JH25A/3JH30A Marine Engines (Replaces 129100-01621) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Free standard shipping on all orders under 1 KG
Gasket, Cover – Fits Yanmar 3JH25A/3JH30A Marine Engines (Replaces ...
Product Details
This is a high-quality replacement Gasket, Cover – Fits Yanmar 3JH25A/3JH30A Marine Engines (Replaces 129100-01621), designed to provide a proper seal for the engine's rear seal cover assembly. It is engineered to meet or exceed original manufacturer specifications, ensuring reliable performance in marine environments.
This part is a direct replacement for Yanmar part number 129100-01621.
- Installation Method: Direct replacement
- Engineered for marine diesel applications
- Includes one cover gasket
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yanmar | 129100-01621 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Yanmar | 3JH25A | 25 | 4-Stroke | 129100-01621 | |
| Yanmar | 3JH30A | 30 | 4-Stroke | 129100-01621 |
Technical Specs
- Product Type
- Gasket, Rear Seal Cover
- Installation
- Direct replacement
- Housing Material
- Paper/Composite
- Other Technical Attributes
- Original manufacturer specification
- Product Dimensions
- 21.0cm L x 20.0cm W x 0.1cm H
What’s in the Box
- 1 x Gasket, Cover (129100-01621)
Installation Notes
- Disconnect the negative battery terminal to prevent accidental shorts.
- If necessary, drain engine oil or coolant to avoid spills when the cover is removed.
- Remove any components obstructing access to the rear seal cover.
- Carefully unbolt and remove the cover. The old gasket may be stuck to the cover or the engine block.
- Thoroughly clean both mating surfaces. Use a plastic scraper and appropriate solvent to remove all traces of old gasket material and sealant without scratching the metal.
- Position the new gasket correctly on the engine block or cover, aligning all bolt holes.
- Reinstall the cover and tighten the bolts in a crossing pattern to the manufacturer's specified torque to ensure even pressure.
- Reinstall any components that were removed. Refill drained fluids.
- Reconnect the battery, start the engine, and carefully inspect for any leaks around the cover.
Troubleshooting & FAQ
How can I confirm this gasket fits my Yanmar engine?
This gasket is a direct fit for Yanmar models 3JH25A and 3JH30A. Verify your engine model and cross-reference the OEM part number 129100-01621. Visually comparing your old gasket to the product images is also a reliable confirmation step.
What are common signs of a failed rear seal cover gasket?
The most common sign of a failed gasket is an oil leak from the area where the rear seal cover meets the engine block. You may notice oil drips under the engine or an accumulation of grime and oil on the housing itself.
Does this gasket require any sealant during installation?
Typically, paper or composite gaskets like this one are designed to be installed dry. However, always consult your engine's service manual. Some applications may recommend a very thin coat of a specific gasket sealant or tackifier to hold it in place during assembly.
How often should this gasket be replaced?
This gasket does not have a set replacement interval. It should be replaced whenever the rear seal cover is removed for service, or if it shows signs of leaking.
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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