Cylinder Head Gasket – Fits Yamaha 8HP/9.9HP 4-Stroke Outboards (Replaces 6G8-11181-A1-00)
Cylinder Head Gasket – Fits Yamaha 8HP/9.9HP 4-Stroke Outboards (Replaces 6G8-11181-A1-00) 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
Cylinder Head Gasket – Fits Yamaha 8HP/9.9HP 4-Stroke Outboards (Re...
Product Details
This replacement Cylinder Head Gasket is designed for Yamaha 4-stroke 8HP and 9.9HP outboard engines manufactured between 1985 and 2005, including F8, T8, F9.9, T9.9, and FT9.9 models. It ensures a precise seal between the cylinder head and the engine block, restoring performance and preventing leaks.
It serves as a direct interchange for Yamaha part numbers 6G8-11181-00-00, 6G8-11181-A0-00, and 6G8-11181-A1-00, as well as Mercury 804004, 825482, and Sierra 18-3827.
- Installation requires removal of the cylinder head.
- Engineered to meet or exceed original equipment manufacturer (OEM) material specifications.
- Package contains one cylinder head gasket.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 6G8-11181-A1-00 | Supersedes 6G8-11181-00-00, 6G8-11181-A0-00 |
| Mercury | 804004 | |
| Mercury | 825482 | |
| Sierra | 18-3827 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
Yamaha models covered include select 8 HP and 9.9 HP 4-stroke outboards from 1985–2005.
This part also fits certain rebranded Mercury 4-stroke outboards in the 8-9.9 HP range, which were manufactured by Yamaha.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F8/T8 | 8 | 4-Stroke | 1985–2005 | 6G8-11181-A1-00 | Previous: 6G8-11181-00-00, 6G8-11181-A0-00 |
| Yamaha | F9.9/T9.9/FT9.9 | 9.9 | 4-Stroke | 1985–2005 | 6G8-11181-A1-00 | Previous: 6G8-11181-00-00, 6G8-11181-A0-00 |
| Mercury | Some 8-9.9HP models | 8-9.9 | 4-Stroke | 804004, 825482 | Rebranded Yamaha engines |
Technical Specs
- Product Type
- Cylinder Head Gasket
- Installation
- Direct replacement, requires cylinder head removal
- Material
- OEM specification
- Dimensions
- 15.0" L x 15.0" W x 0.1" H
- Other Technical Attributes
- Genuine OEM specification
What’s in the Box
- 1 x Gasket, Cylinder Head (Replaces 6G8-11181-A1-00)
Installation Notes
- Disconnect the battery and allow the engine to cool completely. Turn off the fuel supply.
- Remove the engine cover and any components obstructing access to the cylinder head.
- Following the service manual's specified loosening sequence, progressively undo the cylinder head bolts.
- Carefully lift the cylinder head away from the engine block. Avoid using pry tools that could damage the mating surfaces.
- Remove the old gasket. Thoroughly clean both the cylinder head and engine block surfaces of any old gasket material or residue.
- Position the new gasket correctly on the engine block; check for proper alignment with dowel pins and passages.
- Reinstall the cylinder head and tighten the bolts in the sequence and to the torque values specified in your service manual.
- Reassemble all previously removed components and reconnect the battery and fuel lines before testing.
Troubleshooting & FAQ
How do I know if this gasket fits my engine?
This gasket is for Yamaha 8HP & 9.9HP 4-stroke outboards (1985–2005) and some equivalent Mercury models. Always cross-reference your engine's part number with the provided list (6G8-11181-A1-00, 6G8-11181-A0-00, 6G8-11181-00-00) and verify your model in the compatibility table.
What are the signs of a failed cylinder head gasket?
Common symptoms include engine overheating, a noticeable loss of power, white or sweet-smelling smoke from the exhaust, bubbling in the coolant reservoir, or a milky appearance in the engine oil (indicating water contamination).
Can I reuse my old cylinder head bolts?
It is strongly recommended to use new cylinder head bolts. Old bolts can stretch beyond their usable limit ("yield") and may not provide the correct clamping force, leading to premature gasket failure.
Does this gasket require sealant?
No, this gasket is typically installed dry. Applying sealant can interfere with the gasket's ability to create a proper seal. Always consult your engine's official service manual for instructions specific to your model.
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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