Cylinder Block Cover Gasket – Fits Mercury/Mercruiser 65 Jet/75/90 HP 3 Cylinder Outboards (Replaces 27-430057)
Cylinder Block Cover Gasket – Fits Mercury/Mercruiser 65 Jet/75/90 HP 3 Cylinder Outboards (Replaces 27-430057) 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 replacement Cylinder Block Cover Gasket – Fits Mercury/Mercruiser 65 Jet/75/90 HP 3 Cylinder Outboards (Replaces 27-430057) is designed for Mercury and Mercruiser 65 Jet, 75 HP, and 90 HP 3-cylinder 2-stroke outboard engines manufactured between 1987 and 1993. It ensures a precise seal to prevent coolant and exhaust leaks, restoring engine integrity and performance.
It directly replaces Mercury part numbers 27-430057, 27-430056, 27-430055, 27-430053, 27-430052, and 27-430051, and interchanges with Sierra 18-2740, GLM 37660, and EMP 27-27529.
- Installs as a direct replacement for the factory original part.
- Engineered for use in marine gasoline engine environments.
- Meets or exceeds OEM factory original equipment specifications.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Mercury | 27-430057 | Current OEM Part Number |
| Mercury | 27-430056 | Superseded by 27-430057 |
| Mercury | 27-430055 | Superseded by 27-430057 |
| Mercury | 27-430053 | Superseded by 27-430057 |
| Mercury | 27-430052 | Superseded by 27-430057 |
| Mercury | 27-430051 | Superseded by 27-430057 |
| Sierra | 18-2740 | Aftermarket Replacement |
| GLM | 37660 | Aftermarket Replacement |
| EMP | 27-27529 | Aftermarket Replacement |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury engines, this gasket fits specific 3-cylinder models from 1987–1993. Verify your engine's serial number range if multiple are listed.
For Mariner engines, this part fits 75 and 90 HP models across ELH, ELHPTO, ELO, and ELPTO variants produced between 1987 and 1993.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 65 JET | 65 | 2-Stroke | 1987–1993 | 27-430057 | 3 Cylinder |
| Mercury | 65 JET (3 CYL.) | 65 | 2-Stroke | 1993 | 27-430057 | Model 1B000001 & Up |
| Mercury | 75 (3 CYL.) | 75 | 2-Stroke | 1987–1993 | 27-430057 | Multiple serial ranges |
| Mercury | 90 (3 CYL.) | 90 | 2-Stroke | 1987–1993 | 27-430057 | Multiple serial ranges |
| Mariner | 75 | 75 | 2-Stroke | 1987–1993 | 27-430057 | ELH, ELHPTO, ELO, ELPTO variants |
| Mariner | 90 | 90 | 2-Stroke | 1987–1993 | 27-430057 | ELHPTO, ELO, ELPTO variants |
Technical Specs
- Product Type
- Cylinder Block Cover Gasket
- Installation
- Direct replacement
- Fuel Type
- Gasoline
- Dimensions
- 9.5" H x 21.0" W x 0.25" L
- Weight
- 0.25 lb (0.113 kg)
- Other Technical Attributes
- OEM factory original equipment
What’s in the Box
- 1 x Gasket (27-430057)
Installation Notes
- Disconnect the battery and ensure the engine is cool to the touch before starting.
- Drain the engine coolant to a level below the cylinder block cover.
- Carefully remove the bolts and fasteners securing the cylinder block cover.
- Remove the old gasket and thoroughly clean both mating surfaces. Ensure they are free of old gasket material, sealant, oil, and debris.
- Position the new gasket correctly on the cylinder block. Do not use sealant unless specified by your engine’s service manual.
- Reinstall the cylinder block cover and tighten the bolts in the sequence and to the torque specifications recommended by the manufacturer.
- Refill the cooling system, reconnect the battery, and start the engine.
- Check carefully for any coolant or exhaust leaks around the cover.
Troubleshooting & FAQ
How do I confirm this gasket fits my exact engine model?
Your engine's model, year, and serial number are key. Please compare this information against the 'Engine & Model Compatibility' table above. If your engine is listed, the gasket is a confirmed fit. For any uncertainty, we recommend checking your service manual or contacting us with your engine details.
What are the signs of a failing cylinder block cover gasket?
Common symptoms include external coolant or oil leaks from the side of the engine block, engine overheating, or a loss of compression. A visual inspection may reveal gasket material that is brittle, cracked, or squeezed out of place.
Do I need to use any adhesive or sealant with this gasket?
This gasket is designed to be installed dry. Applying sealants can interfere with the seal and may cause it to fail prematurely. Always follow the specific instructions in your engine's official service manual.
When should this gasket be replaced?
Replacement is typically done during a major engine overhaul or if you notice any signs of a leak or failure. It is not a routine maintenance item but should be inspected whenever related engine components are serviced.
What is the difference between this and a genuine Mercury gasket?
While this is an aftermarket part, it is manufactured to meet or exceed OEM specifications using comparable, high-quality materials. It is designed to offer the same performance and reliability as the original equipment part at a better value.
Is this gasket compatible with both 2-stroke and 4-stroke engines?
This specific gasket is engineered only for the 3-cylinder 2-stroke Mercury and Mariner outboard models listed in the compatibility chart. It will not fit 4-stroke engines or models not explicitly listed.
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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