170°F / 77°C Thermostat with Rubber Sealing Ring for MerCruiser 4.3L, 5.0L, 5.7L & 6.2L MPI Engines
170°F / 77°C Thermostat with Rubber Sealing Ring for MerCruiser 4.3L, 5.0L, 5.7L & 6.2L MPI Engines is backordered and will ship as soon as it is back in stock.
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170°F / 77°C Thermostat with Rubber Sealing Ring for MerCruiser 4.3...
170°F / 77°C Thermostat with Rubber Sealing Ring for MerCruiser 4.3L, 5.0L, 5.7L & 6.2L MPI Engines is backordered and will ship as soon as it is back in stock.
Product Details
This replacement 170°F / 77°C thermostat is designed for MerCruiser stern-drive and outboard-drive applications with 4.3L, 5.0L, 5.7L and 6.2L MPI engines. The product includes one thermostat and one rubber sealing ring for a complete thermostat replacement.
The thermostat corresponds to MerCruiser/Mercury OEM reference 864493. The included rubber sealing ring corresponds to 25-807134. Additional reference number: 18-43015.
- 170°F / 77°C operating temperature rating.
- Application range identified for MerCruiser 4.3L, 5.0L, 5.7L and 6.2L MPI engines.
- Includes one thermostat and one rubber sealing ring.
- Verify the engine model, MPI configuration and original part references before ordering.
Part Number Matrix
Use the following references to compare this replacement with the part being removed. The sealing-ring reference applies to the included ring, not to the thermostat itself.
| Component | Brand or Reference Type | Part Number |
|---|---|---|
| Thermostat | MerCruiser/Mercury OEM reference | 864493 |
| Rubber sealing ring | MerCruiser/Mercury OEM reference | 25-807134 |
| Thermostat | Additional reference | 18-43015 |
Engine Compatibility
This thermostat is for the following MerCruiser MPI engine displacements. Exact year, serial-number range, drive configuration and cooling-system configuration are not specified, so confirm those details against your engine identification plate and service information before installation.
| Brand | Engine Displacement | Configuration | Temperature Rating | Reference |
|---|---|---|---|---|
| MerCruiser | 4.3L | MPI | 170°F / 77°C | 864493 |
| MerCruiser | 5.0L | MPI | 170°F / 77°C | 864493 |
| MerCruiser | 5.7L | MPI | 170°F / 77°C | 864493 |
| MerCruiser | 6.2L | MPI | 170°F / 77°C | 864493 |
Technical Specifications
- Product Type
- Engine thermostat with rubber sealing ring
- Temperature Rating
- 170°F / 77°C
- Engine Applications
- MerCruiser 4.3L, 5.0L, 5.7L and 6.2L MPI engines
- Thermostat Reference
- 864493
- Sealing Ring Reference
- 25-807134
- Additional Reference
- 18-43015
- Package Contents
- One thermostat and one rubber sealing ring
What's in the Box
- 1 x 170°F / 77°C thermostat, reference 864493
- 1 x rubber sealing ring, reference 25-807134
Installation Notes
- Allow the engine to cool completely before beginning work.
- Confirm that the replacement thermostat, sealing ring and engine configuration match the original components.
- Remove the thermostat housing according to the engine manufacturer's service procedure.
- Note the orientation of the original thermostat before removal.
- Clean the housing and mating surfaces carefully without damaging them.
- Install the new thermostat and the included rubber sealing ring in the correct orientation.
- Reinstall the thermostat housing and tighten its fasteners to the manufacturer's specified torque.
- Refill or restore the cooling system as required by the engine manufacturer's procedure.
- Run the engine, inspect the housing for leaks and confirm that the temperature remains within the normal operating range.
Troubleshooting & FAQ
What temperature does this thermostat open at?
This thermostat is rated at 170°F / 77°C.
Which engines are listed for this thermostat?
The available product information lists MerCruiser 4.3L, 5.0L, 5.7L and 6.2L MPI engines. Because year and serial-number conditions are not provided, confirm the exact engine application before ordering.
What is included with the thermostat?
The package includes one thermostat and one rubber sealing ring. The thermostat reference is 864493, and the included ring reference is 25-807134.
Is this an OEM thermostat?
This listing is for a replacement thermostat. It is identified by the OEM reference 864493 for application and comparison purposes; it should not be assumed to be a factory-branded OEM component.
How can I confirm fitment for my engine?
Check the engine displacement, MPI configuration and the reference number on the original thermostat. Also compare the engine identification plate and service information, since exact model-year and serial-number ranges are not specified in the available product data.
What are common signs of a thermostat problem?
Possible symptoms include overheating, unusually low operating temperature, slow warm-up or an unstable temperature reading. Diagnose the cooling system before replacing the thermostat.
Safety & Important Information
- Work only on a fully cooled engine and follow the engine manufacturer's service procedure.
- Do not rely on engine displacement alone; verify the MPI configuration and original reference before purchase.
- Do not reuse a damaged or permanently deformed sealing ring.
- Professional installation is recommended when the required service procedure or torque specifications are unavailable.
About Sea Sierra
- Marine Replacement Parts — Parts selected for common marine engine service and replacement applications.
- Application-Focused Listings — Product references and engine applications are provided to support part comparison.
- Practical Service Support — Verify the exact engine configuration and original part before installation.
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