Cylinder Head Gasket – Fits Yamaha 20-25HP 2-Stroke (1988-2009) (Replaces 6L2-11181-A1-00)
Cylinder Head Gasket – Fits Yamaha 20-25HP 2-Stroke (1988-2009) (Replaces 6L2-11181-A1-00) is backordered and will ship as soon as it is back in stock.
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Cylinder Head Gasket – Fits Yamaha 20-25HP 2-Stroke (1988-2009) (Re...
Product Details
This replacement Cylinder Head Gasket – Fits Yamaha 20-25HP 2-Stroke (1988-2009) (Replaces 6L2-11181-A1-00) is engineered to restore a proper seal between the cylinder head and engine block. It is designed for compatibility with Yamaha 20HP and 25HP 2-stroke outboard models with 2-cylinder engines manufactured between 1988 and 2009.
It serves as a direct interchange for Yamaha part numbers 6L2-11181-00-00, 6L2-11181-A1-00, 6L2-11181-A2-00, and 6L2-11181-A3-00, as well as Sierra part 18-3847.
- Engineered for direct replacement installation.
- Designed for gasoline-powered 2-cylinder, 2-stroke outboard engines.
- Built to meet or exceed original factory specifications for a reliable seal.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Yamaha | 6L2-11181-00-00 | 6L2-11181-A1-00 | |
| Yamaha | 6L2-11181-A1-00 | 6L2-11181-A2-00 | Original part number for many models. |
| Yamaha | 6L2-11181-A2-00 | 6L2-11181-A3-00 | |
| Yamaha | 6L2-11181-A3-00 | Current OEM replacement part. | |
| Sierra | 18-3847 | Aftermarket cross-reference. |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket is designed for specific Yamaha 2-stroke engines. Please verify the model code and year range to ensure correct fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 20D, 20DM, 20DEO (6L3) | 20 | 2-Stroke | 1988–1997 | 6L2-11181-A1-00 | Superseded by 6L2-11181-A3-00 |
| Yamaha | 20MLHU, 20MSHU | 20 | 2-Stroke | 1996–1997 | 6L2-11181-A1-00 | Superseded by 6L2-11181-A3-00 |
| Yamaha | 20D, 20DEM, 20MLHZ, 20MSHA, 20MLHB, 20MLHC, 20MLHD, 20MLHE | 20 | 2-Stroke | 1998–2009 | 6L2-11181-A3-00 | Current part |
| Yamaha | 25N, 25D, 25MLH, 25M, 25NM (6L2/6L3/6L20) | 25 | 2-Stroke | 1988–1999 | 6L2-11181-A1-00 | Superseded by 6L2-11181-A3-00 |
| Yamaha | 25ELG, 25ESG, 25LG, 25SG, 25ELF, 25ESF, 25LF, 25SF | 25 | 2-Stroke | 1988–1989 | 6L2-11181-A1-00 | Superseded by 6L2-11181-A3-00 |
| Yamaha | 25ELD, 25ESD, 25LD, 25SD | 25 | 2-Stroke | 1990 | 6L2-11181-A1-00 | Superseded by 6L2-11181-A3-00 |
| Yamaha | 25ELHP, 25ELRP, 25ESHP, 25MLHP, 25MSHP | 25 | 2-Stroke | 1991 | 6L2-11181-A1-00 | Superseded by 6L2-11181-A3-00 |
| Yamaha | 25ELHQ, 25ELRQ, 25ESHQ, 25MLHQ, 25MSHQ | 25 | 2-Stroke | 1992 | 6L2-11181-A1-00 | Superseded by 6L2-11181-A3-00 |
| Yamaha | 25ELHR through 25MSHH series (various suffixes) | 25 | 2-Stroke | 1993–2009 | 6L2-11181-A3-00 | Current part |
Technical Specs
- Product Type
- Cylinder Head Gasket
- Installation
- Direct replacement
- Engine Type
- For 2-cylinder 2-stroke engines
- Fuel Type
- Gasoline
- Dimensions
- 11.0" L x 7.0" W x 0.13" H
- Weight
- 0.06 kg (0.13 lb)
What’s in the Box
- 1 x Cylinder Head Gasket (replaces 6L2-11181-A3-00)
Installation Notes
- Ensure the engine is cool. Disconnect the negative battery terminal and turn off the fuel supply.
- Drain the engine coolant completely into a suitable container.
- Remove any components obstructing access to the cylinder head, such as intake/exhaust manifolds and the valve cover.
- Loosen and remove the cylinder head bolts in the reverse order specified by your service manual to prevent head warping.
- Carefully lift the cylinder head off the engine block. Remove the old head gasket.
- Thoroughly clean both the cylinder head and engine block surfaces of any old gasket material, oil, and debris. Use a plastic scraper to avoid gouging the metal.
- Position the new gasket correctly on the engine block; do not use sealant unless specified by the manufacturer.
- Carefully place the cylinder head back onto the block and install new or inspected head bolts.
- Torque the head bolts in the sequence and to the specifications outlined in your engine's service manual. This is critical for a proper seal.
- Reinstall all previously removed components. Reconnect fuel lines and electrical connectors.
- Refill the cooling system. Reconnect the battery.
- Start the engine and let it warm up, checking carefully for any coolant or oil leaks around the head gasket.
Troubleshooting & FAQ
How do I know if this gasket fits my specific Yamaha engine?
This gasket is not a universal part. It's crucial to verify your engine's model number and year against the compatibility chart provided on this page. It is designed for specific Yamaha 20HP and 25HP 2-stroke outboards from 1988–2009.
What are the common signs of a blown or failing cylinder head gasket?
Symptoms include engine overheating, a noticeable loss of power or compression, milky or discolored engine oil (coolant mixing with oil), white smoke from the exhaust (coolant burning in cylinders), or visible coolant leaks from the engine block/head seam.
Do I need to apply sealant to this gasket during installation?
Generally, no. Modern replacement gaskets like this one are designed to be installed dry. Applying sealants can interfere with the seal. Always consult your official service manual for your specific engine model for the definitive procedure.
What is the difference between part 6L2-11181-A1-00 and the current 6L2-11181-A3-00?
Part number 6L2-11181-A3-00 is the most recent version from Yamaha, which supersedes older part numbers including -A1-00 and -A2-00. Our part is a direct replacement for this entire supersession chain, ensuring compatibility with all listed models.
When should a head gasket be replaced?
A cylinder head gasket must be replaced any time the cylinder head is removed for service. It should also be replaced immediately if you diagnose any signs of failure, such as overheating or loss of compression, to prevent further engine damage.
Can I reuse my old cylinder head bolts?
It is strongly recommended to use new cylinder head bolts. Head bolts can stretch when torqued to yield, and reusing them can result in improper clamping force, leading to premature failure of the new gasket.
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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