Cylinder Block Gasket – Fits Mercury/Mercruiser 40-50 HP (27-85487)
Cylinder Block Gasket – Fits Mercury/Mercruiser 40-50 HP (27-85487) 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
Product Details
This high-quality aftermarket Cylinder Block Gasket – Fits Mercury/Mercruiser 40-50 HP (27-85487) is engineered for a precise seal on Mercury Marine/Mercruiser 40-50 HP 4-cylinder outboard engines from various model years.
It serves as a direct interchange for Mercury part numbers 27-85487, 27-37816, 27-78026, and 27-72487, as well as Sierra cross-reference 18-2507.
- Installation Location: Between the engine block and cylinder head.
- Engineered to provide a durable, leak-free seal under marine conditions.
- Manufactured to meet or exceed original equipment specifications for fit and function.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Mercury | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
| Mercury | 27-37816 | Superseded by 27-85487 |
| Mercury | 27-78026 | Superseded by 27-85487 |
| Mercury | 27-72487 | Superseded by 27-85487 |
| Sierra | 18-2507 | Aftermarket cross-reference for 27-85487 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket is designed for specific 4-cylinder 40 HP and 50 HP engines under the Mercury Marine/Mercruiser brand. Compatibility is determined by serial number range, not specific model years.
| Brand | Model | Rated HP | Stroke | Years / Serial Range | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury Marine/Mercruiser | 45 (4 CYL.) | 45 | 4-Stroke | 5531630 THRU 0B110788 | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
| Mercury Marine/Mercruiser | 45 (4 CYL.) | 45 | 4-Stroke | 7143688 THRU 0A719280 | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
| Mercury Marine/Mercruiser | 45 (4 CYL.) | 45 | 4-Stroke | 8063985 & Up | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
| Mercury Marine/Mercruiser | 45 (4 CYL.) | 45 | 4-Stroke | 9248006 THRU 9466691 | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
| Mercury Marine/Mercruiser | 50 (4 CYL.) | 50 | 4-Stroke | 5531630 & Up | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
| Mercury Marine/Mercruiser | 50 (4 CYL.) | 50 | 4-Stroke | 7143688 & Up | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
| Mercury Marine/Mercruiser | 50 (4 CYL.) | 50 | 4-Stroke | 8063985 & Up | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
| Mercury Marine/Mercruiser | 50 (4 CYL.) | 50 | 4-Stroke | 9248006 & Up | 27-85487 | Supersedes 27-37816, 27-78026, 27-72487 |
Technical Specs
- Product Type
- Cylinder Block Gasket
- Installation
- Engine block-to-cylinder
- Dimensions
- 14.0" × 7.0" × 0.25"
- Weight
- 0.03 kg (0.06 lbs)
What’s in the Box
- 1 x Gasket (27-85487)
Installation Notes
- Disconnect the battery and ensure the engine is completely cool before starting.
- Drain the engine coolant system as per your owner's manual.
- Carefully remove the cylinder head cover, cylinder head, and any other interfering components, noting their order and orientation.
- Remove the old cylinder block gasket and discard it.
- Thoroughly clean both the engine block and cylinder head mating surfaces. Ensure they are perfectly flat and free of old gasket material, sealant, oil, and debris.
- Place the new gasket into position, confirming correct alignment with all coolant passages, oil galleries, and bolt holes. Do not use sealant unless explicitly required by your engine's service manual.
- Reinstall the cylinder head. Torque the head bolts in the precise sequence and torque stages specified by the manufacturer's service manual to ensure an even seal.
- Reassemble all other components, refill the cooling system, and reconnect the battery.
- Start the engine and let it warm up. Carefully check for any coolant, oil, or exhaust leaks around the cylinder head seam.
Troubleshooting & FAQ
How do I know if my cylinder block gasket is failing?
Common signs of a bad gasket include engine overheating, white smoke from the exhaust (burning coolant), milky or discolored engine oil (coolant mixing with oil), and unexplained coolant loss without visible external leaks.
Will this gasket fit my specific engine serial number?
This part is designed for the specified Mercury 40-50 HP 4-cylinder models and fits a wide range of serial numbers. Please review the Engine & Model Compatibility table to confirm your engine's serial number falls within the listed ranges.
What is the difference between this aftermarket gasket and an OEM one?
This aftermarket gasket is engineered to meet or exceed OEM specifications for fit, material composition, and durability. It provides comparable performance and sealing capability, offering a cost-effective solution for engine repair.
Is any sealant required for installation?
Most modern gaskets of this type are designed to be installed dry. However, always consult your engine's official service manual. Some specific applications or older models may recommend a light, non-hardening sealant.
How often should a cylinder block gasket be replaced?
This is not a regular maintenance part. Gaskets are typically replaced only when the cylinder head is removed for other service or if the gasket itself has failed and is causing performance issues.
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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