Gasket – Fits Mercury/Mercruiser 3.7L, 470, 485 (Replaces 27-99960)
Gasket – Fits Mercury/Mercruiser 3.7L, 470, 485 (Replaces 27-99960) 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.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Gasket – Fits Mercury/Mercruiser 3.7L, 470, 485 (Replaces 27-99960)
Product Details
This end cap and heat exchanger Gasket – Fits Mercury/Mercruiser 3.7L, 470, 485 (Replaces 27-99960), and is designed for engine models manufactured between 1976 and 1989. It is engineered for use with 4-inch heat exchangers, ensuring a dependable seal to prevent coolant leaks.
This part is a direct interchange for Mercury/Mercruiser 99960, Sierra 18-0389, and Skcvmn 99960.
- Installation Location: End Cap, Heat Exchanger
- Specific Design: Made for 4-inch heat exchangers
- Warranty: Includes a 1-year factory warranty against defects
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Mercury / Mercruiser | 99960 |
| Sierra | 18-0389 |
| Skcvmn | 99960 |
Engine & Model Compatibility
Confirm your engine model and year/serial range in the table below.
The models listed below under the Mercury brand are part of the Mercruiser product line. They are grouped here for clarity based on source data and consistent OEM part number usage.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 165 | I/L4 | 1987 (0B434941 THRU 0B774251) | 27-99960 | Carbureted (2 BBL.) | |
| Mercury | 170 | I/L4 | 1985–1986 (6916779 THRU 0B434940) | 27-99960 | Carbureted (2 BBL.) | |
| Mercury | 180 | I/L4 | 1987 (0B436391 THRU 0B775248) | 27-99960 | Carbureted (4 BBL.) | |
| Mercury | 190 | I/L4 | 1985–1986 (6916779 THRU 0B436390) | 27-99960 | Carbureted (4 BBL.) | |
| Mercury | 3.7L | I/L4 | 1988–1989 (0B774252 & Up) | 27-99960 | Carbureted (2 BBL.) | |
| Mercury | 3.7LX | I/L4 | 1988–1989 (0B775249 & Up) | 27-99960 | Carbureted (4 BBL.) | |
| Mercury | 470 | I/L4 | 1976–1979 (4208730 THRU 5520114) | 27-99960 | Carbureted (2 BBL.) | |
| Mercury | 470 | I/L4 | 1980–1982 (5520115 THRU 6218036) | 27-99960 | Carbureted (2 BBL.) | |
| Mercury | 470 | I/L4 | 1983–1984 (6218037 THRU 6916778) | 27-99960 | Carbureted (2 BBL.) | |
| Mercury | 470 MIE | I/L4 | 1980–1981 (5520115 THRU 6218036) | 27-99960 | Inboard Exhaust | |
| Mercury | 485 | I/L4 | 1980–1982 (5685394 THRU 6218036) | 27-99960 | Carbureted (2 BBL.) | |
| Mercury | 488 | I/L4 | 1983–1984 (6170297 THRU 6916778) | 27-99960 | Carbureted (4 BBL.) |
Technical Specs
- Product Type
- Gasket
- Installation
- End Cap, Heat Exchanger
- Housing Color
- Black
- Dimensions
- L: 0.19 in x W: 6.0 in x H: 7.5 in
- Weight
- 0.1875 lb (0.085 kg)
- Warranty
- 1 year factory warranty against defects and workmanship
- Other Technical Attributes
- Designed for 4-inch heat exchanger
What’s in the Box
- 1 x GASKET (27-99960 / 99960)
Installation Notes
- Disconnect the battery and ensure the engine is cool.
- Drain the engine coolant from the heat exchanger into a suitable container.
- Carefully remove the bolts securing the heat exchanger end cap.
- Remove the end cap and pry away the old gasket. Be careful not to gouge the metal surfaces.
- Thoroughly clean both the end cap and the heat exchanger mating surfaces to remove any old gasket material or corrosion.
- Position the new gasket onto the heat exchanger.
- Reinstall the end cap and tighten the bolts to the manufacturer's recommended torque specifications.
- Refill the cooling system with the correct type and amount of coolant.
- Reconnect the battery, start the engine, and carefully check for any leaks around the end cap.
Troubleshooting & FAQ
How can I confirm this gasket is the right one for my engine?
The most reliable method is to check your engine's model, year, and serial number against the compatibility table above. The serial number ranges provided are critical for confirming fitment, especially for models produced across many years.
What are the typical signs of a failing heat exchanger gasket?
Common symptoms include external coolant leaks (often visible as drips or residue around the end cap), engine overheating, or milky/contaminated engine oil if there's an internal breach.
Should I use sealant or adhesive with this gasket?
This type of gasket is typically designed to be installed dry. Applying sealant can sometimes cause it to slip out of place during installation. Always consult your engine's official service manual for specific instructions.
What is the difference between this and the OEM part?
This listing is an aftermarket replacement, not an OEM part. It is engineered to meet or exceed original equipment specifications, using comparable materials and manufacturing processes to offer reliable performance at a better value.
How fast do you ship and what are the costs?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free to most regions, with expedited options available at checkout for an additional fee where applicable.
What is the warranty and return policy?
This part is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard window for unused items in their original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against 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 quality control.
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