Cylinder Head Gasket – Fits Yanmar 6LP Series Marine Diesel (Replaces 119771-00421)
Cylinder Head Gasket – Fits Yanmar 6LP Series Marine Diesel (Replaces 119771-00421) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Cylinder Head Gasket – Fits Yanmar 6LP Series Marine Diesel (Replac...
Product Details
This is a high-quality aftermarket Cylinder Head Gasket – Fits Yanmar 6LP Series Marine Diesel engines, including the STE, STZE, STZE1, STZY, STZYJ, WST, and WSTZY models. Designed for marine applications, this gasket ensures a perfect seal between the cylinder head and the engine block for 6.0L, 315–480 HP diesel engines.
It serves as a direct replacement for Yanmar part number 119771-00421 (Mark 5 version) and aftermarket equivalent AM119771-00421.
- Installs between the cylinder head and engine block.
- Constructed from durable multi-layer steel/composite materials.
- This is the newer Mark 5 design for enhanced performance and reliability.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yanmar | 119771-00421 | Mark 5 version |
| Aftermarket | AM119771-00421 | Direct replacement |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yanmar Marine Diesel engines, this gasket fits the 6LP and 6LPA series. Verify your specific model against the compatibility list.
| Brand | Model | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|
| Yanmar | 6LP-ST | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LP-STE | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LP-STZE | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LP-STZE1 | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LP-STZY | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LP-STZYJ | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LP-WST | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LP-WSTZY | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LPA-STP | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LPA-STP2 | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LPA-STZP2 | 4-Stroke | 119771-00421 | Mark 5 version |
| Yanmar | 6LPA-STZP3 | 4-Stroke | 119771-00421 | Mark 5 version |
Technical Specs
- Product Type
- Cylinder Head Gasket
- Installation
- Between cylinder head and engine block
- Fuel Type
- Diesel
- Housing Material
- Multi-layer steel/composite
- Dimensions
- 66.0" L x 18.5" W x 1.0" H
- Other Technical Attributes
- Mark 5 version (newer design)
What’s in the Box
- 1 x Cylinder Head Gasket (119771-00421)
Installation Notes
- Ensure the engine is cool and disconnect the battery. Drain the cooling system completely.
- Disconnect all hoses, electrical connectors, and exhaust components from the cylinder head.
- Following the manufacturer's service manual, loosen the cylinder head bolts in the specified sequence to prevent warping.
- Carefully lift the cylinder head off the engine block. Avoid damaging the surfaces.
- Thoroughly clean both the cylinder head and engine block surfaces. Remove all old gasket material, sealant, and debris.
- Place the new head gasket onto the engine block, ensuring it aligns with the locating dowels. Do not use sealant unless specified by the engine manufacturer.
- Carefully lower the cylinder head back into place over the gasket and dowels.
- Install new or cleaned cylinder head bolts and torque them in the correct pattern and sequence as specified in your service manual.
- Reconnect all components, refill the cooling system, and check for leaks before starting the engine.
Troubleshooting & FAQ
How do I know if I need the Mark 5 version?
The Mark 5 (119771-00421) is the latest revision for the Yanmar 6LP series, superseding older versions like Mark 1 and Mark 3. It is backward compatible. If your engine is in the 6LP or 6LPA family, this gasket is the correct updated part.
Can I reuse my old cylinder head bolts?
It is strongly recommended to use new torque-to-yield (TTY) bolts during a head gasket replacement, as they are designed to stretch upon installation and may not provide adequate clamping force if reused. Always consult your engine's service manual for specific guidance.
What are the signs of a failed head gasket?
Common symptoms include engine overheating, white smoke from the exhaust (coolant burning), milky or foamy engine oil, loss of coolant with no visible leaks, and bubbles in the radiator or coolant overflow tank. A compression or leak-down test can confirm the failure.
Do I need to apply any sealant to this gasket?
No. This multi-layer steel (MLS) gasket is designed to be installed dry. Applying sealants can interfere with its ability to seal correctly and may cause premature failure. Always ensure mating surfaces are perfectly clean and dry.
What is the difference between this and older gasket versions?
The Mark 5 incorporates design and material improvements for better sealing and durability compared to the Mark 1 (119771-00401) and Mark 3 (119771-00411) versions. It is the most current and reliable option for these engines.
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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