Thermostat Repair Service Kit – Fits Mercury/MerCruiser 4.3L 5.0L 5.7L 7.4L V6 V8 SternDrive Motors (Replaces 807252Q4, 807252T4, 807252T7, 8M0089715)
Thermostat Repair Service Kit – Fits Mercury/MerCruiser 4.3L 5.0L 5.7L 7.4L V6 V8 SternDrive Motors (Replaces 807252Q4, 807252T4, 807252T7, 8M0089715) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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
Thermostat Repair Service Kit – Fits Mercury/MerCruiser 4.3L 5.0L 5...
Product Details
This Thermostat Repair Service Kit – Fits Mercury/MerCruiser 4.3L 5.0L 5.7L 7.4L V6 V8 SternDrive Motors is designed for gasoline sterndrive engines (262-454 CID) from 1983 to 2016 with standard cooling systems. It ensures proper engine temperature regulation for optimal performance and longevity.
It serves as a direct cross-reference for Mercury/MerCruiser part numbers 807252Q4, 807252T4, 807252T7, 8M0089715 and aftermarket equivalents from Sierra (18-3668), GLM (13390), and Mallory (9-43150).
- Features a 140°F (60°C) nominal opening temperature.
- Engineered for V6 and V8 engines with standard (raw water) cooling systems.
- Includes all necessary gaskets and an O-ring 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.
For MerCruiser models, check your engine’s model year range or serial number to ensure an exact match.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | 4.3L V6 175/185/205 | 175–205 | 4-Stroke | 1985–1987 | 807252Q4 | Model years 0A331455–0B775129 |
| MerCruiser | 4.3L V6 | 175–205 | 4-Stroke | 1987–1995 | 807252Q4 | Model years 0B773243–0F601126 |
| MerCruiser | 5.0L & 5.7L Small Block | 200–260 | 4-Stroke | 1983–1984 | 807252Q4 | Model years 6218462–6899057 |
| MerCruiser | 5.0L | 200–230 | 4-Stroke | 1988–1995 | 807252Q4 | Model years 0B774445–0F600999 |
| MerCruiser | 5.0LX | 230 | 4-Stroke | 1988–1995 | 807252Q4 | Model years 5907058–0F600999 |
| MerCruiser | 5.7L/5.7MIE/SKI | 260–350 | 4-Stroke | 1988–1995 | 807252Q4 | Model years 0B773305–0F600999 |
| MerCruiser | 7.4L/MIE | 330–340 | 4-Stroke | 1988–1994 | 807252Q4 | Model years 0B771113–0F351999 |
| MerCruiser | GM V6 & V8 | Various | 4-Stroke | 1983–2016 | 807252Q4 | Standard cooling systems only |
Technical Specs
- Product Type
- Thermostat Kit
- Installation
- Standard Cooling System
- Operating Temperature
- 140°F (60°C) nominal opening
- Housing Material
- Brass
- Housing Color
- Silver/Metallic
- Weight
- 0.11 kg (0.25 lb)
- Warranty
- 1-year (aftermarket)
- Other Technical Attributes
- Not for use with high-performance engines
What’s in the Box
- 1 x Thermostat (8M6002714/59137)
- 1 x O-Ring (25-30224)
- 1 x Gasket Thermostat Housing Cover (27-33179-2)
- 1 x Gasket Thermostat Cover (27-41812)
- 1 x Gasket Thermostat Housing (27-47510)
- 1 x Gasket Lower Housing (27-530451/27-48818-1)
- 1 x Gasket (27-33918)
Installation Notes
- Ensure the engine is completely cool before beginning work.
- Locate the thermostat housing, typically where the large upper radiator hose connects to the engine.
- Drain coolant from the engine block to a level below the housing.
- Remove the bolts holding the thermostat housing cover.
- Take out the old thermostat, noting its orientation.
- Thoroughly clean all old gasket material from the housing and cover mating surfaces.
- Install the new thermostat in the correct orientation, followed by the appropriate new gasket or O-ring from the kit.
- Re-install the housing cover and tighten the bolts to the manufacturer's specified torque.
- Refill the cooling system with the correct type and amount of coolant.
- Start the engine, check for any leaks, and monitor the temperature gauge to ensure the thermostat opens correctly.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs of a faulty thermostat include engine overheating, running too cold (temperature gauge stays low), erratic temperature readings, or coolant leaks from the thermostat housing area.
What is the correct operating temperature for this part?
This thermostat is designed to start opening at a nominal temperature of 140°F (60°C), making it suitable for raw water-cooled marine engines in various conditions.
Can this kit be used with a closed (freshwater) cooling system?
No, this kit is specified for use with standard (raw water) cooling systems only. Using it in the wrong application can lead to improper engine temperatures.
Is it necessary to replace all the included gaskets?
Yes. For a reliable, leak-free seal, you must replace the old gaskets and O-ring with the new components provided. Mating surfaces must be clean and dry before installing new gaskets.
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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