140°F Thermostat Kit for MerCruiser GM V6/V8 Engines, 4.3L–8.2L
140°F Thermostat Kit for MerCruiser GM V6/V8 Engines, 4.3L–8.2L is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
140°F Thermostat Kit for MerCruiser GM V6/V8 Engines, 4.3L–8.2L
140°F Thermostat Kit for MerCruiser GM V6/V8 Engines, 4.3L–8.2L is backordered and will ship as soon as it is back in stock.
Product Details
This 140°F thermostat kit is designed for selected MerCruiser GM V6 and V8 marine engines using a standard raw-water cooling system. It covers a range of 4.3L, 5.0L, 5.7L, 7.4L, 7.9L and 8.2L applications listed below. The thermostat opens at approximately 140°F (60°C) to help regulate engine operating temperature.
The kit is listed as a replacement for MerCruiser 807252Q4 and 807252T4, Sierra 18-3668, GLM 13390, Quicksilver 75-03948 and Barr 59137. Confirm the thermostat temperature, housing style and complete engine serial number before ordering.
- 140°F (60°C) opening temperature.
- For selected standard raw-water cooling applications.
- Designed for specified MerCruiser GM V6 and V8 engines.
- Includes the thermostat and gasket components listed in the box contents below.
Part Number Matrix
These references are provided for cross-reference purposes. They should be checked against the engine model, serial number and cooling-system configuration.
| Brand | Part Number |
|---|---|
| MerCruiser | 807252Q4 / 807252T4 |
| Sierra | 18-3668 |
| GLM | 13390 |
| Quicksilver | 75-03948 |
| Barr | 59137 |
Engine & Model Compatibility
The following MerCruiser applications and serial ranges are associated with the referenced thermostat application. Model, year, horsepower, displacement and serial conditions must be considered together. If your engine falls outside these listings, consult the engine service manual before purchasing.
| Model | Rated HP | CID/Liters | Years | OEM Part No. | Serial or application notes |
|---|---|---|---|---|---|
| 175 (V6) | 175 | 262 (4.3L) | 1987 | 807252Q4 | 0B527955–0B773242 |
| 185 (V6) | 185 | 229 | 1983–1984 | 807252Q4 | 6330183–6919655 |
| 185 (V6) | 185 | 262 (4.3L) | 1985–1986 | 807252Q4 | 0A331455–0B527954 |
| 205 (V6) | 205 | 262 (4.3L) | 1985–1987 | 807252Q4 | 0B527955–0B775129 |
| 4.3L (V6) | Various | 262 (4.3L) | 1987–1995 | 807252Q4 | 0B773243–0F601126 |
| 4.3L/LX (V6) | Various | 262 (4.3L) | 1993–1995 | 807252Q4 | 0F000878–0F601126 |
| 898 (V8) | Various | 305 (5.0L) | 1983–1984 | 807252Q4 | 6218462–689905 |
| 200 (V8) | 200 | 305 (5.0L) | 1985–1987 | 807252Q4 | 6899058–0B774444 |
| 228 (V8) | 228 | 305 (5.0L) | 1982–1984 | 807252Q4 | 6218462–6899268 |
| 230 (V8) | 230 | 305 (5.0L) | 1985–1987 | 807252Q4 | 6899269–0B773739 |
| 230 MIE (V8) | 230 | 305 (5.0L) | 1981–1987 | 807252Q4 | 5907058–0B78151 |
| 5.0L (V8) | Various | 305 (5.0L) | 1988–1995 | 807252Q4 | 0B774445–0F600999 |
| 5.0L MIE (V8) | Various | 305 (5.0L) | 1988 | 807252Q4 | 0B788152–0C396832 |
| 5.0LX (V8) | Various | 305 (5.0L) | 1988–1995 | 807252Q4 | 5907058–0F600999 |
| 260 (V8) | 260 | 350 (5.7L) | 1982–1987 | 807252Q4 | 6218462–0B788151 |
| 260 MIE (V8) | 260 | 350 (5.7L) | 1981–1987 | 807252Q4 | 5907058–0B788151 |
| 300 (V8) | 300 | 350 (5.7L) | 1985–1986 | 807252Q4 | 6668677–0B430367 |
| 300 Mag (V8) | 300 | 350 (5.7L) | 1986–1995 | 807252Q4 | 0A635178–0F600999 |
| 350 MAG (V8) | 350 | 350 (5.7L) | 1986–1995 | 807252Q4 | 0A635178–0F600999 |
| 350 MAG (V8) | 350 | 350 (5.7L) | 1987–1995 | 807252Q4 | 0B525982–0F600999 |
| 350 MAG Ski | 350 | 350 (5.7L) | 1991–1996 | 807252Q4 | 0D505450–0K040399 |
| 5.7L (V8) | Various | 350 (5.7L) | 1988–1995 | 807252Q4 | 0B773305–0F600999 |
| 5.7L MIE (V8) | Various | 350 (5.7L) | 1988–1995 | 807252Q4 | 0B788152–0F600999 |
| 5.7L Ski (V8) | Various | 350 (5.7L) | 1985–1995 | 807252Q4 | 0A338533–0F775199 |
| 330 MIE (V8) | 330 | 454 (7.4L) | 1977–1987 | 807252Q4 | 4623115–0B816540 |
| 340 MIE (V8) | 340 | 454 (7.4L) | 1981–1992 | 807252Q4 | 5889914–0D715493 |
| 370 (V8) | 370 | 454 (7.4L) | 1985–1987 | 807252Q4 | 6721528–0B714586 |
| 454 MAG Alpha/Bravo | Various | 454 (7.4L) | 1986–1994 | 807252Q4 | 0A631894–0F304999 |
| 525 SC (V8) | 525 | 454 (7.4L) | 1991–1999 | 807252Q4 | 0D456000–0L415623 |
| 7.4L (V8) | Various | 454 (7.4L) | 1988–1994 | 807252Q4 | 0B771113–0F351999 |
| 7.4L MIE (V8) | Various | 454 (7.4L) | 1988–1994 | 807252Q4 | 0B788366–0F349999 |
| 390 MCM & MIE | 390 | 482 (7.9L) | 1969–1970 | 807252Q4 | 2781129–3042731 |
| 460 (V8) | 460 | 482 (7.9L) | 1983–1986 | 807252Q4 | 4179554–6181046 |
| 465 (V8) | 465 | 502 (8.2L) | 1990–1994 | 807252Q4 | 0C849992–0F213244 |
| 500, 500 EFI | 500 | 502 (8.2L) | 1994–2004 | 807252Q4 | 0F213293 and later |
| 502 MAG | Various | 502 (8.2L) | 1990–1993 | 807252Q4 | 0C878221–0F114528 |
| 8.2L MIE | Various | 502 (8.2L) | 1990–1992 | 807252Q4 | 0C878221–0D857199 |
Technical Specifications
- Product Type
- Engine thermostat kit
- Thermostat Rating
- 140°F (60°C)
- Application
- Selected standard raw-water cooling systems
- Compatibility
- Selected MerCruiser GM V6 and V8 engines from approximately 4.3L through 8.2L, subject to model and serial-number conditions
- Thermostat Diameter
- Approximately 54 mm
- Housing or Sleeve
- A brass sleeve may be used on some applications, but it is not included unless specifically listed in the package contents
What's in the Box
- 1 × thermostat, referenced as 807252T1 / 59137
- 1 × O-ring, 25-30224
- 1 × gasket, 27-33179-2
- 1 × gasket, 27-47510
- 1 × gasket, 27-41812
A brass sleeve such as 23-47508T is used on some applications but is not included in the listed contents of this kit. Reuse the original sleeve only if the engine requires one and it is in serviceable condition.
Installation Notes
- Disconnect the boat battery and allow the engine to cool before beginning work.
- Drain coolant or raw water from the thermostat housing area as required by the engine service procedure.
- Remove the bolts securing the thermostat housing cover.
- Note the orientation of the original thermostat, sleeve and gasket before removal.
- Remove the old thermostat and clean the housing and engine mating surfaces.
- Install the new thermostat in the correct orientation with the appropriate new gasket or O-ring from the kit.
- Reinstall the housing cover and tighten the fasteners to the engine manufacturer's specified torque.
- Restore the cooling system using the correct procedure for the engine's cooling configuration.
- Reconnect the battery, start the engine and inspect carefully for leaks as it warms.
- Verify that the engine reaches its expected operating temperature and that cooling water flow is normal.
Troubleshooting & FAQ
How do I know whether my engine needs a 140°F or another temperature thermostat?
This kit is intended for applications specified for a 140°F thermostat. Some closed-cooling or freshwater-cooled configurations use a different temperature rating. Check the owner's or service manual and confirm the exact engine serial number before installation.
What are common signs of a failing thermostat?
A thermostat stuck closed can contribute to overheating, while one stuck open can prevent the engine from reaching its intended operating temperature. Either condition can affect engine performance and cooling-system operation.
Why are multiple gaskets included?
The listed applications use different thermostat housing and sealing arrangements. The gasket assortment is intended to cover the specified applications; use only the gasket or O-ring that matches the engine housing.
Is the brass sleeve required?
Not every application uses a brass sleeve. Check the original assembly and the engine service manual. This kit includes only the parts listed in the box-contents section and does not include a brass sleeve unless separately stated.
Is this an OEM part?
This listing is for an aftermarket replacement kit. The cross-reference numbers identify the related OEM and aftermarket applications; they do not indicate that this kit is manufactured by MerCruiser or another OEM brand.
What should I verify before ordering?
Verify the engine brand, model, horsepower, displacement, stroke or engine configuration where applicable, cooling-system type, thermostat temperature and complete serial-number range. Do not rely on displacement alone because different production ranges can use different components.
What is the warranty?
Warranty coverage, if applicable, is governed by the seller's current warranty and returns policy. Review the policy in effect at the time of purchase.
Safety & Important Information
- Always compare the original thermostat, housing and sealing arrangement with the replacement before installation.
- Do not install a 140°F thermostat in an application specified for a different temperature rating.
- Confirm the complete engine serial number and cooling-system configuration before ordering.
- Use the manufacturer's service procedure and specified fastener torque.
- Professional installation is recommended when the correct application or cooling-system configuration is uncertain.
About Sea Sierra
- Marine Replacement Parts — We supply replacement components for a range of marine engine and cooling-system applications.
- Application-Focused Listings — Product references and fitment details are provided to help customers compare the replacement with the original part.
- Customer Support — When fitment is uncertain, provide the engine model, year and complete serial number before ordering.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
