Cylinder Head Gasket – Fits Yanmar 2GM20 Series (Replaces 128271-01911)
Cylinder Head Gasket – Fits Yanmar 2GM20 Series (Replaces 128271-01911) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Cylinder Head Gasket – Fits Yanmar 2GM20 Series (Replaces 128271-01...
Product Details
This aftermarket Cylinder Head Gasket – Fits Yanmar 2GM20 Series (Replaces 128271-01911) is designed for Yanmar 2-cylinder marine diesel engines (18-20 HP) manufactured between 1983 and 2005. It fits the 2GM20, 2GM20F, 2GM20-YEU, and 2GM20F-YEU series.
It serves as a direct replacement for Yanmar part number 128271-01911 and Sierra aftermarket part 18-55602, ensuring a reliable seal for your engine's cylinder head.
- Engineered for direct replacement installation.
- Constructed from a durable, non-asbestos composite material suitable for marine diesel environments.
- Manufactured in Japan to meet or exceed OEM specifications.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yanmar | 128271-01911 |
| Sierra | 18-55602 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket is designed for specific Yanmar marine diesel engines. Please verify compatibility with your model and part number before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yanmar | 2GM20 | 18 | 4-Stroke | 1983–2005 | 128271-01911 | |
| Yanmar | 2GM20F | 18 | 4-Stroke | 1983–2005 | 128271-01911 | Fresh water cooled version |
| Yanmar | 2GM20-YEU | 18 | 4-Stroke | 1983–2005 | 128271-01911 | |
| Yanmar | 2GM20F-YEU | 18 | 4-Stroke | 1983–2005 | 128271-01911 | Fresh water cooled version |
| Yanmar | 2GMLP | 18 | 4-Stroke | 1983–2005 | 128271-01911 | Low profile variant |
Technical Specs
- Product Type
- Cylinder Head Gasket
- Installation
- Direct replacement
- Fuel Type
- Diesel
- Housing Material
- Non-asbestos composite
- Dimensions
- 20.0" L x 14.5" W x 0.2" H
- Bore Diameter
- 75 mm
- Warranty
- 6 months (manufacturer warranty)
- Country of Origin
- Japan (OEM)
What’s in the Box
- 1 x Cylinder Head Gasket (Replaces 128271-01911)
Installation Notes
- Ensure the engine is completely cool. Disconnect the negative battery terminal.
- Drain the engine coolant completely.
- Remove the valve cover, rocker arm assembly, and pushrods in sequence. Keep them organized.
- Loosen and remove the cylinder head bolts in the reverse order of the manufacturer's tightening sequence.
- Carefully lift the cylinder head off the engine block. Do not pry between the head and block mating surfaces.
- Remove the old head gasket and thoroughly clean both the cylinder head and engine block surfaces. Ensure they are free of any old gasket material, sealant, oil, or debris.
- Position the new cylinder head gasket correctly over the dowel pins on the engine block. Do not use any sealant unless explicitly required by the service manual.
- Carefully lower the cylinder head back onto the block and gasket.
- Install and tighten the cylinder head bolts in the correct sequence and to the torque specifications found in your engine's service manual. This is critical for a proper seal.
- Reassemble the pushrods, rocker arm assembly, valve cover, and all other components.
- Refill the cooling system with the recommended coolant type.
- Reconnect the battery, start the engine, and carefully check for any coolant, oil, or compression leaks.
Troubleshooting & FAQ
How do I know if my cylinder head gasket is failing?
Common signs of a blown head gasket include engine overheating, white smoke from the exhaust (burning coolant), milky or foamy engine oil (coolant contamination), loss of compression, or coolant being pushed out of the reservoir.
Is this gasket compatible with the Yanmar 2GMLP model?
Yes, this cylinder head gasket is confirmed to be compatible with the Yanmar 2GMLP low-profile variant, as it uses the same OEM part number 128271-01911.
Should I use sealant when installing this gasket?
Generally, modern composite gaskets like this one are designed to be installed dry without any additional sealants. Applying sealant can interfere with the gasket's ability to create a proper seal. Always follow the specific instructions in your official Yanmar service manual.
What are the signs of an incorrect installation?
Immediate signs of a bad installation include coolant or oil leaks around the cylinder head, engine misfires, or immediate overheating. Failure to follow the correct bolt tightening sequence and torque values is a common cause of installation failure.
What is the difference between an OEM and an aftermarket part?
This listing is for an aftermarket replacement, not an original equipment manufacturer (OEM) part. It has been engineered to meet or exceed OEM-level specifications using comparable materials. Our parts are manufactured in an ISO 9002 certified facility and are batch-inspected for quality and consistency.
What are your shipping speeds and costs?
We ship worldwide quickly, with a typical transit time of 5–15 days for most regions. Standard shipping is free. Expedited shipping options, where available, will be presented at checkout.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter any issues, please contact our support team with your order details. Unused items in their original condition can be returned within our standard return window. Please see our policy page or contact us for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchasing. If anything differs—even if your model is listed as compatible—do not purchase.
- This is an aftermarket replacement component, not an OEM part.
- Professional installation is strongly recommended for safety, performance, and to prevent engine damage.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with an average transit time of 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.
Payment & Security
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