Thermostat Gasket – Fits Mercury MerCruiser V6/V8 (Replaces 27-48818Q01)
Thermostat Gasket – Fits Mercury MerCruiser V6/V8 (Replaces 27-48818Q01) is backordered and will ship as soon as it is back in stock.
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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
Thermostat Gasket – Fits Mercury MerCruiser V6/V8 (Replaces 27-4881...
Product Details
This high-quality Thermostat Gasket – Fits Mercury MerCruiser V6/V8 (Replaces 27-48818Q01) ensures a reliable seal between the thermostat and its housing. It is designed for Mercury MerCruiser V6 and V8 GM engines with standard cooling systems from 1982 and older, as well as high-performance models up to 1996.
It serves as a direct replacement for multiple part numbers, including Sierra 18-2844, GLM 31510, Mallory 9-60010, Mercury 27-48818Q01, and several OMC equivalents.
- Engineered for gasoline marine engines with standard cooling systems.
- Installs directly between the thermostat and the thermostat housing.
- Package contains one thermostat gasket for a complete replacement.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Sierra | 18-2844 |
| GLM | 31510 |
| Mallory | 9-60010 |
| Mercury | 27-48818 |
| Mercury | 27-488181 |
| Mercury | 27-48818Q01 |
| OMC | 0508562 |
| OMC | 0508566 |
| OMC | 0508619 |
| OMC | 0508717 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket is designed for MerCruiser V6 and V8 GM engines with standard cooling systems, covering models from 1982 and older, plus high-performance variants up to 1996.
The listed OMC part numbers are for cross-reference purposes. Verify fitment against your specific engine model before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | V8 engines | Various | 4-Stroke | 1982 and older | 27-48818Q01 | Standard cooling system |
| MerCruiser | V6 engines | Various | 4-Stroke | 1982 and older | 27-48818Q01 | Standard cooling system |
| MerCruiser | High Performance | Various | 4-Stroke | Up to 1996 | 27-48818Q01 | Models with standard cooling |
| OMC | Various | Various | 4-Stroke | 0508562/0508566/0508619/0508717 | Cross-reference only |
Technical Specs
- Product Type
- Thermostat Gasket
- Installation
- Between thermostat and housing
- Fuel Type
- Gasoline
- Housing Material
- Paper/Composite
- Dimensions
- 6.0" L x 7.5" W x 0.13" H
- Weight
- Approximately 0.01 kg (0.02 lbs)
- Warranty
- Manufacturer standard warranty
- Other Technical Attributes
- Designed for standard cooling systems
What’s in the Box
- 1 x Thermostat Gasket (27-48818Q01)
Installation Notes
- Disconnect the battery and ensure the engine has completely cooled before starting work.
- Drain the engine coolant to a level below the thermostat housing to prevent spills.
- Carefully loosen and remove the bolts that secure the thermostat housing.
- Remove the old thermostat and gasket. Thoroughly clean both mating surfaces, ensuring no old gasket material or residue remains.
- Position the new thermostat correctly within the engine block or housing.
- Place the new gasket into position, ensuring it aligns with the bolt holes and sealing surfaces.
- Reinstall the thermostat housing and tighten the bolts to the manufacturer's recommended torque in a star pattern.
- Refill the cooling system with the appropriate coolant, check for leaks, and run the engine to confirm proper operation.
Troubleshooting & FAQ
How do I know if this gasket will fit my engine?
This gasket fits MerCruiser V6/V8 GM engines (1982 & older) and high-performance models (up to 1996) with standard cooling. Always match your engine's OEM part number (27-48818Q01) to the references in our Part Number Matrix.
What are the signs of a failing thermostat gasket?
Common signs include coolant leaks around the thermostat housing, engine overheating, or fluctuating engine temperature readings. A visual inspection may reveal cracking or deterioration of the old gasket.
Can I reuse my old gasket?
No. Thermostat gaskets are single-use components designed to crush and create a seal. Always use a new gasket when replacing the thermostat or servicing the housing to prevent leaks.
Do I need sealant with this gasket?
This paper/composite gasket is typically designed to be installed dry. Applying sealants can sometimes cause the gasket to slip or fail prematurely. Always follow your engine's service manual recommendations.
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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