140°F Thermostat Kit for MerCruiser V6 and V8 Engines – Replaces 807252Q4
140°F Thermostat Kit for MerCruiser V6 and V8 Engines – Replaces 807252Q4 is backordered and will ship as soon as it is back in stock.
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140°F Thermostat Kit for MerCruiser V6 and V8 Engines – Replaces 80...
140°F Thermostat Kit for MerCruiser V6 and V8 Engines – Replaces 807252Q4 is backordered and will ship as soon as it is back in stock.
Product Details
This 140°F thermostat kit is designed for General Motors-based MerCruiser V6 and V8 marine engines using a standard cooling system and a 140°F thermostat. The listed applications cover 262–454 CID engines from approximately 1983 through 2016. Always confirm the engine model, serial number, cooling-system configuration, and original thermostat before ordering. This kit is not intended for high-performance variants unless the engine manufacturer specifies the same thermostat application.
It is listed as a replacement for Mercury/Quicksilver 807252Q4 and other aftermarket reference numbers, including Sierra 18-3668 and GLM 13390.
- 140°F (60°C) nominal opening temperature.
- For specified MerCruiser V6 and V8 applications with standard cooling systems.
- Kit contents are listed below; gasket and seal configuration can vary by application.
Part Number Matrix
Use these references to compare the thermostat kit with your original part and catalog information. A reference number alone does not confirm fitment for every engine model.
| Brand | Part Number |
|---|---|
| Mercury/Quicksilver | 807252Q4 |
| Mercury/Quicksilver | 807252T4 |
| Mercury/Quicksilver | 807252T7 |
| Mercury/Quicksilver | 8M0089715 |
| Sierra | 18-3668 |
| GLM | 13390 |
| Mallory | 9-43150 |
Engine and Model Compatibility
The following applications are listed for this 140°F thermostat kit. Keep the model, year, horsepower, stroke, and serial-number conditions together when checking fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Serial or Application Notes |
|---|---|---|---|---|---|---|
| MerCruiser | 4.3L V6 175/185/205 | 175–205 | 4-Stroke | 1985–1987 | 807252Q4 | 0A331455–0B775129 |
| MerCruiser | 4.3L V6 | 175–205 | 4-Stroke | 1987–1995 | 807252Q4 | 0B773243–0F601126 |
| MerCruiser | 4.3L/LX GM | 175–205 | 4-Stroke | 1993–1995 | 807252Q4 | 0F000878–0F601126 |
| MerCruiser | 5.0L and 5.7L Small Block | 200–260 | 4-Stroke | 1983–1984 | 807252Q4 | 6218462–6899057 |
| MerCruiser | 5.0L | 200–230 | 4-Stroke | 1988–1995 | 807252Q4 | 0B774445–0F600999 |
| MerCruiser | 5.0LX | 230 | 4-Stroke | 1988–1995 | 807252Q4 | 5907058–0F600999 |
| MerCruiser | 5.7L/5.7MIE/SKI | 260–350 | 4-Stroke | 1988–1995 | 807252Q4 | 0B773305–0F600999 |
| MerCruiser | 5.7L Ski | 260–350 | 4-Stroke | 1985–1995 | 807252Q4 | 0A338533–0F775199 |
| MerCruiser | 7.4L/MIE | 330–340 | 4-Stroke | 1988–1994 | 807252Q4 | 0B771113–0F351999 |
| MerCruiser | 8.2L MIE | 380+ | 4-Stroke | 1990–1992 | 807252Q4 | 0C878221–0D857199 |
Technical Specifications
- Product Type
- Thermostat kit
- Thermostat Rating
- 140°F (60°C)
- Nominal Opening Temperature
- 140°F (60°C)
- Cooling System
- Standard cooling system applications
- Thermostat Construction
- Brass sleeve
- Fitment Limitation
- Not intended for high-performance engines unless the application specifically requires this thermostat
What's in the Box
The listed kit components are:
- 1 x Thermostat, 8M6002714/59137
- 1 x O-ring, 25-30224
- 1 x Thermostat housing-cover gasket, 27-33179-2
- 1 x Thermostat-cover gasket, 27-41812
- 1 x Thermostat-housing gasket, 27-47510
- 1 x Lower-housing gasket, 27-530451/27-48818-1
- 1 x Gasket, 27-33918, where required by the applicable kit configuration
Because housing and gasket arrangements differ between engine applications, compare the supplied components with the parts removed from your engine before installation.
Installation Notes
- Allow the engine to cool completely and disconnect the battery before starting work.
- Drain coolant or raw water to a level below the thermostat housing as applicable to the cooling-system design.
- Remove the bolts securing the thermostat housing, keeping track of brackets, hoses, and the original gasket arrangement.
- Remove the old thermostat, gasket, and O-ring. Discard removed seals.
- Clean the housing and manifold mating surfaces thoroughly, removing old gasket material and corrosion without damaging the sealing surfaces.
- Install the new thermostat in the same orientation as the original and use the applicable new gasket or O-ring.
- Reinstall the housing and tighten the fasteners to the engine manufacturer's specified torque.
- Refill the cooling system as required. Start the engine, allow it to reach operating temperature, and check the housing and hose connections for leaks.
Troubleshooting and FAQ
How do I confirm that this thermostat kit fits my engine?
Compare your complete engine model, year, horsepower, stroke, serial-number range, cooling-system configuration, and original thermostat reference with the compatibility information on this page. Do not rely on the engine family or a single reference number alone.
What are common signs of a failing marine thermostat?
Possible symptoms include overheating, an engine that runs cooler than expected, erratic temperature readings, or leakage near the thermostat housing. Inspect the complete cooling system before replacing the thermostat.
What is the difference between a 140°F and a 160°F thermostat?
The temperature rating indicates the approximate temperature at which the thermostat begins to open. A 140°F thermostat is commonly used in certain raw-water or saltwater-cooled marine applications, while other closed-cooling applications may specify a higher rating. Always use the temperature specified for your engine.
Do I need to replace every gasket in the package?
Use the gasket or O-ring that matches your engine's thermostat-housing configuration. Replace the old applicable seals during installation, but do not install extra gaskets that are not used by your housing design.
How often should a marine thermostat be replaced?
Inspect the thermostat during routine cooling-system maintenance and replace it if it is corroded, stuck, damaged, or associated with abnormal engine temperature. Saltwater exposure and cooling-system contamination can shorten service life.
Is this an OEM part?
No. This is an aftermarket replacement kit intended to replace the listed OEM and aftermarket reference numbers. Confirm the application and component configuration before installation.
How is the kit shipped?
Available shipping methods, delivery estimates, and costs are shown at checkout and may vary by destination.
What should I do if the kit does not match my engine?
Do not force the thermostat or install mismatched gaskets. Compare the original component, engine identification, and applicable reference numbers, then contact support before installation if the configuration differs.
Safety and Important Information
- Work only on a cool engine and follow the engine manufacturer's safety procedures.
- Verify the engine model, serial number, cooling-system type, original thermostat, and gasket arrangement before ordering.
- Compare the supplied parts with the removed parts before installation.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended when the cooling-system configuration or fitment is uncertain.
About Sea Sierra
- Pro-Grade Standards — Marine replacement parts selected for dependable service in real-world conditions.
- Global Fulfillment — Shipping options and delivery estimates are provided at checkout.
- Value-Focused Parts — Practical aftermarket solutions for routine marine maintenance and repair.
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