Thermostat Service Kit for Mercury MerCruiser Sterndrive Engines – Replaces 807252Q4 and 807252T4
Thermostat Service Kit for Mercury MerCruiser Sterndrive Engines – Replaces 807252Q4 and 807252T4 is backordered and will ship as soon as it is back in stock.
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Thermostat Service Kit for Mercury MerCruiser Sterndrive Engines – ...
Thermostat Service Kit for Mercury MerCruiser Sterndrive Engines – Replaces 807252Q4 and 807252T4 is backordered and will ship as soon as it is back in stock.
Product Details
This thermostat service kit is designed for selected Mercury MerCruiser sterndrive cooling-system applications. It provides a replacement thermostat together with the gaskets and O-ring needed to service the thermostat and housing sealing surfaces.
The kit replaces Mercury MerCruiser OEM part numbers 807252Q4 and 807252T4. Confirm the engine model, cooling-system design, and serial-number range before ordering because thermostat and gasket requirements can vary between MerCruiser applications.
- Complete thermostat service kit for the listed application.
- Includes one thermostat, three thermostat-cover gaskets, one O-ring, and one thermostat-housing gasket.
- Thermostat specification: approximately 142°F (61°C) nominal rating.
- Intended for the corresponding MerCruiser sterndrive cooling-system configuration; it is not a universal V6/V8 kit.
Part Number Matrix
These are verified replacement and aftermarket reference numbers for this kit. Reference numbers identify the intended part relationship; they do not replace an application check.
| Brand | Part Number | Role |
|---|---|---|
| Mercury MerCruiser | 807252Q4 | OEM replacement reference |
| Mercury MerCruiser | 807252T4 | OEM replacement reference |
| Sierra | 18-3668 | Aftermarket thermostat kit reference |
Engine & Model Compatibility
Compatibility must be confirmed using the complete engine model, cooling-system arrangement, and serial number. The replacement references above are associated with selected MerCruiser sterndrive thermostat-kit applications, but a general engine-family description alone is not sufficient to confirm fitment.
| Brand | Application | Cooling System | Thermostat Rating | Fitment Check |
|---|---|---|---|---|
| Mercury MerCruiser | Selected sterndrive thermostat applications using OEM references 807252Q4 or 807252T4 | Confirm the specific raw-water or closed-cooling configuration before installation | Approximately 142°F (61°C) | Verify engine model and serial number against the applicable service catalog |
Technical Specs
- Product Type
- Thermostat service kit
- Application
- Selected Mercury MerCruiser sterndrive cooling-system applications
- Nominal Thermostat Rating
- Approximately 142°F (61°C)
- OEM Replacement References
- 807252Q4 and 807252T4
- Aftermarket Reference
- Sierra 18-3668
- Fitment Requirement
- Match engine model, cooling-system configuration, and serial number before ordering
What’s in the Box
- 1 x Thermostat
- 1 x Thermostat cover gasket, reference 27-47510
- 1 x Thermostat cover gasket, reference 27-48818-1
- 1 x Thermostat cover gasket, reference 27-60208
- 1 x O-ring
- 1 x Thermostat housing gasket, reference 27-53045-1 or 27-33918
Gasket shapes and required sealing locations depend on the corresponding housing design. Use only the gasket that matches the removed component and the service-manual installation arrangement.
Installation Notes
- Allow the engine to cool completely before servicing the thermostat housing.
- Close any seacock or isolate the water supply as required by the boat and engine service procedure.
- Locate the thermostat housing and remove the cover or housing components according to the engine service manual.
- Record the original thermostat orientation before removal.
- Remove the old thermostat, O-ring, and gaskets. Do not reuse compressed or damaged sealing components.
- Clean and dry the mating surfaces without scratching the housing or cover.
- Install the new thermostat in the original orientation and fit the appropriate new gaskets and O-ring from the kit.
- Reassemble the housing and tighten fasteners to the engine manufacturer’s specified torque.
- Restore the cooling-water supply and operate the engine according to the service procedure.
- Check for leaks and confirm that the engine reaches and maintains its normal operating temperature.
Troubleshooting & FAQ
Which OEM numbers does this kit replace?
This kit is listed as a replacement for Mercury MerCruiser OEM numbers 807252Q4 and 807252T4.
What thermostat temperature rating is included?
The associated thermostat is approximately 142°F (61°C). Do not substitute a different temperature rating unless it is specified for your exact engine application.
Does the kit include the thermostat and seals?
Yes. The kit includes one thermostat, three thermostat-cover gaskets, one O-ring, and one thermostat-housing gasket.
Can I use this kit on any Mercury MerCruiser V6 or V8?
No. MerCruiser thermostat designs and gasket requirements vary by engine model, cooling-system arrangement, and serial number. Confirm all three before ordering.
Should the old gaskets or O-ring be reused?
No. Replace the removed sealing components with the matching new components supplied in the kit, and clean the mating surfaces before assembly.
Is this an OEM Mercury MerCruiser part?
This listing is for an aftermarket service kit. The OEM numbers are provided as replacement references only.
Safety & Important Information
- Work only on a completely cool engine and follow the applicable marine-engine service procedure.
- Verify the engine model, cooling-system configuration, serial number, thermostat rating, and gasket arrangement before purchase and installation.
- Do not rely on engine displacement or cylinder count alone to confirm fitment.
- Professional installation is recommended when the correct housing arrangement or cooling-system type is uncertain.
About Sea Sierra
- Marine Replacement Parts — We provide aftermarket components and service kits for common marine cooling-system repairs.
- Application-Focused Listings — OEM replacement references are shown to help customers compare the part with the component being replaced.
- Installation-Conscious Support — Always match the engine model, serial number, and cooling-system configuration before installation.
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