Seal – Fits Mercury MerCruiser 4.5L/5.0L/6.2L Engines (Replaces 25-8M0084884, 866152)
Seal – Fits Mercury MerCruiser 4.5L/5.0L/6.2L Engines (Replaces 25-8M0084884, 866152) 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).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Seal – Fits Mercury MerCruiser 4.5L/5.0L/6.2L Engines (Replaces 25-...
Product Details
This cooler Seal – Fits Mercury MerCruiser 4.5L/5.0L/6.2L Engines is designed for a precise fit on various MerCruiser MPI engines, specifically models produced between 2010 and 2014. It functions as a critical gasket for the heat exchanger, ensuring a leak-free seal for optimal cooling system performance.
It serves as a direct aftermarket replacement for Mercury part numbers 25-8M0084884, 866152, and 864707.
- Designed for direct, hassle-free installation.
- Functions as a cooler and exchanger gasket seal.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By |
|---|---|---|
| Mercury | 864707 | 866152 |
| Mercury | 866152 | 8M0084884 |
| Mercury | 25-8M0084884 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This part is designed for the following MerCruiser Stern Drive and Inboard engine models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| MerCruiser | 4.5L MPI Alpha/Bravo | 200, 250 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 4.5L MPI Alpha/Bravo EC | 200, 250 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 5.0L Alpha/Bravo MPI | Various | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 5.0L BR DTS MPI | Various | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI | 300, 350 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI Bravo | Various | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI EC | 300, 350 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI EC TOW | 320, 370 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI JET | 370 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI MIE | 300, 350 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI MIE EC | 300, 350 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI TOW | 320, 370 | 4-Stroke | 2010–2014 | 25-8M0084884 |
| MerCruiser | 350 MAG MPI | Various | 4-Stroke | 1998–2010 | 25-8M0084884 |
| MerCruiser | 350 MAG MPI DTS | Various | 4-Stroke | 1998–2010 | 25-8M0084884 |
| MerCruiser | 350 MAG DTS HORIZ | Various | 4-Stroke | 1998–2010 | 25-8M0084884 |
| MerCruiser | 350 MAG HORIZ DTS | Various | 4-Stroke | 1998–2010 | 25-8M0084884 |
| MerCruiser | 350 MAG MPI HORIZ | Various | 4-Stroke | 1998–2010 | 25-8M0084884 |
| MerCruiser | 350 MAG MPI SKI | Various | 4-Stroke | 1998–2010 | 25-8M0084884 |
| MerCruiser | 383 MAG STROKER BRAVO | Various | 4-Stroke | 1998–2010 | 25-8M0084884 |
| MerCruiser | 5.7L | Various | 4-Stroke | 1998–2014 | 25-8M0084884 |
| MerCruiser | 5.7L DTS HORIZ | Various | 4-Stroke | 1998–2014 | 25-8M0084884 |
| MerCruiser | 5.7L MPI DTS | Various | 4-Stroke | 1998–2014 | 25-8M0084884 |
| MerCruiser | 6.2L DTS HORIZ | Various | 4-Stroke | 1998–2014 | 25-8M0084884 |
| MerCruiser | 6.2L HORIZ DTS | Various | 4-Stroke | 1998–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI DTS | Various | 4-Stroke | 1998–2014 | 25-8M0084884 |
| MerCruiser | 6.2L MPI HORIZ | Various | 4-Stroke | 1998–2014 | 25-8M0084884 |
Technical Specs
- Product Type
- Cooler Seal
- Installation
- Direct replacement
- Dimensions
- Height: 2.0 in; Width: 13.0 in; Length: 15.0 in
- Weight
- 0.06 lb (0.027 kg)
- Other Technical Attributes
- Exchanger gasket/seal
What’s in the Box
- 1 x Seal (25-8M0084884)
Installation Notes
- Ensure the engine is off and completely cool. Disconnect the battery.
- Drain the engine cooling system to a level below the heat exchanger or cooler assembly.
- Carefully disconnect hoses and remove any mounting bolts securing the cooler/exchanger end caps.
- Remove the old seal. Thoroughly clean the mating surfaces, ensuring they are free of old gasket material, corrosion, or debris.
- Position the new seal correctly in the groove. Ensure it sits flat and is not twisted.
- Reinstall the end cap, torquing bolts to the manufacturer's specified value and pattern.
- Reconnect all hoses and refill the cooling system with the appropriate coolant.
- Reconnect the battery, start the engine, and carefully check for any leaks as it warms up.
Troubleshooting & FAQ
How do I confirm this is the right seal for my engine?
The best way is to match your engine's model and year against our compatibility table. Also, cross-reference your existing part number with the numbers listed in our Part Number Matrix (25-8M0084884, 866152, 864707). If in doubt, visually compare your old seal to our product images.
What are the signs of a failing cooler seal?
Common symptoms include visible coolant leaks (often green, pink, or yellow fluid) around the heat exchanger housing, engine overheating, or a low coolant warning light. In severe cases, you might notice coolant mixed in with the engine oil (milky appearance), which requires immediate attention.
Do I need to use a sealant or adhesive with this gasket?
No, this seal is designed to create a compression fit and should not require any additional silicone, RTV, or other sealants. Applying foreign substances can interfere with proper seating and may cause premature failure.
How often should this seal be replaced?
There is no fixed replacement interval. It should be replaced whenever the heat exchanger is serviced or if any signs of leaking or degradation are observed during routine inspections.
Is this part for a raw water or closed cooling system?
This seal is typically used in the heat exchanger component of a closed cooling (freshwater) system, separating the internal engine coolant from the external raw water used to cool it.
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.
Payment & Security
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