Thermostat Kit 140°F (60°C) – Fits MerCruiser 4.3L, 5.0L, 5.7L, 7.4L, 8.2L (Replaces 807252Q4, 807252T4, 807252T7)
Thermostat Kit 140°F (60°C) – Fits MerCruiser 4.3L, 5.0L, 5.7L, 7.4L, 8.2L (Replaces 807252Q4, 807252T4, 807252T7) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat Kit 140°F (60°C) – Fits MerCruiser 4.3L, 5.0L, 5.7L, 7.4...
Product Details
This Thermostat Kit 140°F (60°C) – Fits MerCruiser 4.3L, 5.0L, 5.7L, 7.4L, 8.2L is engineered for MerCruiser sterndrive and inboard engines using standard cooling systems. It is specifically designed for V6 4.3L engines from 1987 to 1995 and V8 engines in 5.0L, 5.7L, 7.4L, and 8.2L displacements from 1982 to 1999.
It serves as a direct replacement for Mercury/MerCruiser part numbers 807252Q4, 807252T4, 807252T7, and 8M0089715, as well as Sierra 18-3668, GLM 13390, and Mallory 9-43150.
- Engineered for direct OEM-replacement installation.
- Designed for standard (raw water) cooling systems only.
- Includes thermostat and all necessary gaskets for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/MerCruiser | 807252Q4 |
| Mercury/MerCruiser | 807252T4 |
| Mercury/MerCruiser | 807252T7 |
| Mercury/MerCruiser | 8M0089715 |
| Sierra | 18-3668 |
| GLM | 13390 |
| Mallory | 9-43150 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | 185 (2 BBL.) GM 262 V6 | 185 | 4-Stroke | 1985–1986 | 807252Q4 | Serial 0A331455-0B527954 |
| MerCruiser | 205 (4 BBL.) GM 262 V6 | 205 | 4-Stroke | 1985–1987 | 807252Q4 | Serial 0B527955-0B775129 |
| MerCruiser | 4.3L (2 BBL.) GM 262 V6 | - | 4-Stroke | 1987–1995 | 807252Q4 | Serial 0B773243-0D714106 |
| MerCruiser | 4.3L (GEN II) (2 BBL.) GM 262 V6 | - | 4-Stroke | 1991–1995 | 807252Q4 | Serial 0D714107-0F601126 |
| MerCruiser | 4.3L MPI Alpha/Bravo EC | - | 4-Stroke | 2001–Up | 8M0089715 | Serial 1A637496-Up |
| MerCruiser | 4.3LX (4 BBL.) GM 262 V6 | - | 4-Stroke | 1987–1991 | 807252Q4 | Serial 0B775130-0D714369 |
| MerCruiser | 4.3LX (GEN II) (4 BBL.) GM 262 V6 | - | 4-Stroke | 1991–1995 | 807252Q4 | Serial 0D714370-0F601126 |
| MerCruiser | 200 (2 BBL.) GM 305 V8 | 200 | 4-Stroke | 1983–1987 | 807252Q4 | Serial 6218462-0B774444 |
| MerCruiser | 228 (4 BBL.) GM 305 V8 | 228 | 4-Stroke | 1982–1984 | 807252Q4 | Serial 5170009-0B525981 |
| MerCruiser | 228 MIE (4 BBL.) GM 305 V8 | 228 | 4-Stroke | 1982–1984 | 807252Q4 | Serial 5170009-5907057 |
| MerCruiser | 230 (4 BBL.) GM 305 V8 | 230 | 4-Stroke | 1982–1987 | 807252Q4 | Serial 6218462-0B773739 |
| MerCruiser | 230 MIE (4 BBL.) GM 305 V8 | 230 | 4-Stroke | 1981–1987 | 807252Q4 | Serial 5907058-0B788151 |
| MerCruiser | 5.0L (2 BBL.) GM 305 V8 | - | 4-Stroke | 1987–1995 | 807252Q4 | Serial 0B774445-0F600999 |
| MerCruiser | 5.0L MIE (4 BBL.) GM 305 V8 | - | 4-Stroke | 1987–1988 | 807252Q4 | Serial 0B522506-0B788151 |
| MerCruiser | 5.0L Carb Alpha/Bravo | - | 4-Stroke | 2001–Up | 8M0089715 | Serial 0W650000-Up |
| MerCruiser | 5.0LX (4 BBL.) GM 305 V8 | - | 4-Stroke | 1987–1995 | 807252Q4 | Serial 0B773740-0F600999 |
| MerCruiser | 898 (2 BBL.) GM 305 V8 | 198 | 4-Stroke | 1983–1984 | 807252Q4 | Serial 6218462-0B525981 |
| MerCruiser | 260 (4 BBL.) GM 350 V8 | 260 | 4-Stroke | 1982–1987 | 807252Q4 | Serial 4908850-0B773739 |
| MerCruiser | 260 MIE GM 350 V8 | 260 | 4-Stroke | 1981–1987 | 807252Q4 | Serial 5907058-0B788196 |
| MerCruiser | 350 MAG. (SKI) GM 350 V8 | - | 4-Stroke | 1991–1996 | 807252Q4 | Serial 0D505450-0K040399 |
| MerCruiser | 350 MAG. Alpha (4 BBL.) GM 350 V8 | - | 4-Stroke | 1986–1995 | 807252Q4 | Serial 0A635178-0F600999 |
| MerCruiser | 5.7L GM 350 V8 | - | 4-Stroke | 1982–1995 | 807252Q4 | Serial 0B525982-0F600999 |
| MerCruiser | 5.7L MIE GM 350 V8 | - | 4-Stroke | 1987–1995 | 807252Q4 | Serial 0B788197-0F622099 |
| MerCruiser | 5.7L Carb Alpha/Bravo | - | 4-Stroke | 2001–Up | 8M0089715 | Serial 0W650000-Up |
| MerCruiser | 5.7L MIE GM 350 V8 | - | 4-Stroke | 1995–1997 | 8M0089715 | Serial 0F622151-0F746099 |
| MerCruiser | 5.7L Competition Ski GM 350 V8 | - | 4-Stroke | 1985–1995 | 807252Q4 | Serial 0B514627-0F775199 |
| MerCruiser | 340 MIE W/B/W GM 454 V8 | 340 | 4-Stroke | 1981–1987 | 807252Q4 | Serial 5889914-0B788365 |
| MerCruiser | 370 TRS GM 454 V8 | 370 | 4-Stroke | 1984–1987 | 807252Q4 | Serial 4179554-6721527 |
| MerCruiser | 454 MAG. Bravo GM 454 V8 | - | 4-Stroke | 1986–1991 | 807252Q4 | Serial 0B721206-0D805068 |
| MerCruiser | 454 MAG. Bravo (GEN. V) GM 454 V8 | - | 4-Stroke | 1991–1994 | 807252Q4 | Serial 0D805069-0F304999 |
| MerCruiser | 7.4L Bravo GM 454 V8 | - | 4-Stroke | 1988–1991 | 807252Q4 | Serial 0B771113-0D603117 |
| MerCruiser | 7.4L Bravo (GEN. V) GM 454 V8 | - | 4-Stroke | 1991–1996 | 807252Q4 | Serial 0D603118-0F800699 |
| MerCruiser | 7.4L MIE W/B/W GM 454 V8 | - | 4-Stroke | 1988–1991 | 807252Q4 | Serial 0B788366-0D715493 |
| MerCruiser | 7.4L MIE (LH) GEN. V GM 454 V8 | - | 4-Stroke | 1991–1996 | 807252Q4 | Serial 0D715494-0F820141 |
| MerCruiser | 7.4L MIE w/ Hurth GM 454 V8 | - | 4-Stroke | 1988–1991 | 8M0089715 | Serial 0C391564-0D715493 |
| MerCruiser | 460 TRS GM 482 V8 | 460 | 4-Stroke | 1983–1986 | 8M0089715 | Serial 4179554-6181046 |
| MerCruiser | 500 (GEN. +) GM 502 V8 | 500 | 4-Stroke | 1999–2000 | 8M0089715 | Serial 0L414639-0L601036 |
| MerCruiser | 500 (GEN. VI) GM 502 V8 | 500 | 4-Stroke | 1996–1998 | 8M0089715 | Serial 0K000001-0L000737 |
| MerCruiser | 500 EFI GM 502 V8 | 500 | 4-Stroke | 1998–2004 | 8M0089715 | Serial 0L001496-0L602036 |
| MerCruiser | 500 EFI GM 502 V8 | 500 | 4-Stroke | 2004 | 8M0089715 | Serial 0M050001-0M050853 |
| MerCruiser | 500 EFI GM 502 V8 | 500 | 4-Stroke | 2004 | 8M0089715 | Serial 0M052001-0M053628 |
| MerCruiser | 500 EFI GM 502 V8 | 500 | 4-Stroke | 2005–2006 | 8M0089715 | Serial 0M900064-0M901284 |
| MerCruiser | 500 EFI GM 502 V8 | 500 | 4-Stroke | 2005–2006 | 8M0089715 | Serial 0M905089-0M907127 |
| MerCruiser | 502 MAG. Bravo (GEN. V) GM 502 V8 | - | 4-Stroke | 1990–1993 | 807252Q4 | Serial 0D824589-0F114528 |
Technical Specs
- Product Type
- Thermostat Kit with Gaskets
- Installation
- Direct OEM Replacement
- Temperature Rating
- 140°F (60°C)
- Housing Material
- High-temperature Resistant Brass
- Seal Material
- Silicone
- Weight
- 0.18 lbs (0.08 kg)
- Fitting Type
- Standard MerCruiser Mounting
- Operating Temperature
- 140°F (60°C) Opening Temperature
- Warranty
- Limited Lifetime (Sierra)
- Other Technical Attributes
- For standard cooling systems only (non-high performance)
What’s in the Box
- 1 x Thermostat (807252T1)
- 1 x Thermostat Housing Gasket (27-47510)
- 1 x Upper Housing Gasket (27-53045-1)
- 1 x Cover Gasket (27-41812)
- 1 x Lower Housing Gasket (27-33179-2)
- 1 x O-ring (25-30224)
Installation Notes
- Ensure the engine is completely cool before starting. Disconnect the battery for safety.
- Locate the thermostat housing on the engine, typically where the main coolant hose connects to the engine block.
- Place a drain pan under the housing and slowly loosen the bolts to drain the coolant from the housing.
- Remove the housing bolts and the housing itself. Note the orientation of the old thermostat.
- Remove the old thermostat and any old gasket material from the housing and engine block surfaces.
- Install the new thermostat in the correct orientation. Install the new gaskets as required.
- Reinstall the housing and tighten the bolts to the manufacturer's specified torque.
- Reconnect the coolant hose, refill the cooling system with the appropriate coolant, and check for leaks.
- Reconnect the battery, start the engine, and allow it to reach operating temperature, monitoring the temperature gauge and checking for leaks.
Troubleshooting & FAQ
How do I know if this thermostat is correct for my engine?
The best method is to confirm your engine's original part number matches one listed in our Part Number Matrix. Additionally, you can check your engine model, year, and serial number against the detailed compatibility table on this page.
What are the common signs of a failing thermostat?
A thermostat can fail in two ways: stuck open or stuck closed. If it's stuck open, your engine may run too cool and never reach its proper operating temperature. If it's stuck closed, your engine will overheat, which can cause serious damage.
Is this 140°F thermostat correct for my cooling system?
This 140°F (60°C) thermostat is designed for engines with standard (raw water) cooling systems. Engines with closed (freshwater) cooling systems typically require a higher temperature thermostat (e.g., 160°F). Always use the temperature rating specified by your engine's manufacturer.
Does this kit include everything I need for the job?
This kit includes the thermostat and a comprehensive set of gaskets for the housing assembly. You will need your own tools and coolant to complete the installation.
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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