140°F Marine Thermostat Kit for MerCruiser V6/V8 4.3–8.2L — Replaces Mercury/MerCruiser 807252Q4, 807252T4, 807252T7, 8M0089715
140°F Marine Thermostat Kit for MerCruiser V6/V8 4.3–8.2L — Replaces Mercury/MerCruiser 807252Q4, 807252T4, 807252T7, 8M0089715 is backordered and will ship as soon as it is back in stock.
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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.
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140°F Marine Thermostat Kit for MerCruiser V6/V8 4.3–8.2L — Replace...
140°F Marine Thermostat Kit for MerCruiser V6/V8 4.3–8.2L — Replaces Mercury/MerCruiser 807252Q4, 807252T4, 807252T7, 8M0089715 is backordered and will ship as soon as it is back in stock.
Product Details
This 140°F marine thermostat kit is designed for specified Mercury MerCruiser V6 and V8 gasoline stern-drive engines from 4.3L through 8.2L. It is intended for standard cooling systems and is not listed for high-performance or racing applications. Always confirm the exact engine model and serial-number range before ordering.
The kit is listed as a replacement for several Mercury/MerCruiser and aftermarket references, including Mercury/MerCruiser 807252Q4, 807252T4, 807252T7, and 8M0089715, Sierra 18-3668, GLM 13390, and Mallory 9-43150.
- 140°F (60°C) thermostat for compatible marine gasoline engines.
- Designed for standard MerCruiser cooling systems.
- Includes the thermostat and listed seals and gaskets for installation.
- Aftermarket replacement; not an original Mercury/MerCruiser component.
Part Number Matrix
Use these references when comparing the replacement with the part currently installed on your engine. A part-number match does not replace verification of the engine model and serial range.
| Brand | Part Number |
|---|---|
| Mercury/MerCruiser | 807252Q4 |
| Mercury/MerCruiser | 807252T4 |
| Mercury/MerCruiser | 807252T7 |
| Mercury/MerCruiser | 8M0089715 |
| Sierra | 18-3668 |
| GLM | 13390 |
| Mallory | 9-43150 |
Engine and Model Compatibility
The following applications are the listed fitment scope. Confirm the model, horsepower, year, and serial-number range against your engine's identification plate and service information before installation.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Serial-Number Range |
|---|---|---|---|---|---|---|
| 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
- 140°F thermostat kit
- Temperature Rating
- 140°F (60°C)
- Installation
- Standard cooling system
- Application
- Specified MerCruiser V6 and V8 gasoline engines, excluding high-performance applications
- Housing Material
- Metal/brass
- Weight
- 0.08 kg (0.18 lb)
- Warranty
- 1-year aftermarket warranty
What's in the Box
- 1 × Thermostat, 8M6002714
- 1 × O-ring, 25-30224
- 1 × Thermostat housing-cover gasket, 27-33179-2
- 1 × Thermostat-cover gasket, 27-41812
- 1 × Thermostat-housing gasket, 27-47510
- 1 × Lower-housing gasket, 27-530451 / 27-48818-1
- 1 × Gasket, 27-33918
Installation Notes
- Disconnect the battery and allow the engine to cool completely.
- Place a suitable container beneath the engine and drain the cooling system as required.
- Remove the bolts securing the thermostat housing and remove the housing.
- Remove the old thermostat and gaskets. Clean all mating surfaces thoroughly, removing debris and old gasket material.
- Install the new thermostat in the correct orientation for your engine, then position the appropriate new gaskets and O-ring.
- Reinstall the thermostat housing and tighten the fasteners to the torque specified in the engine service manual. Do not overtighten.
- Refill the cooling system with the correct coolant or coolant mixture for the engine.
- Reconnect the battery, start the engine, bring it to operating temperature, and inspect the housing area for leaks.
Troubleshooting and FAQ
How do I confirm that this thermostat kit fits my engine?
Compare your exact MerCruiser model, horsepower, year, and serial number with the compatibility table. Serial-number ranges must be kept together with the corresponding model and year because fitment can vary within a model family.
What are the symptoms of a failing thermostat?
Possible symptoms include overheating, unusually low operating temperature, slow warm-up, fluctuating temperature readings, or coolant leakage near the thermostat housing. A thermostat stuck closed can cause rapid overheating, while one stuck open can prevent the engine from reaching normal operating temperature.
Why use a 140°F thermostat?
The 140°F rating is used in certain raw-water-cooled marine applications. It helps the engine operate at the temperature specified for the cooling-system design. Always use the temperature rating recommended for your exact engine and cooling system.
Is this kit compatible with high-performance engines?
No. This listing is intended for the standard-duty MerCruiser applications shown in the compatibility table. High-performance and racing engines may use different thermostat designs, cooling arrangements, or temperature ratings.
Is this an OEM part?
No. This is an aftermarket replacement intended to replace the listed Mercury/MerCruiser and aftermarket references. Confirm dimensions, seals, and application details against the original part before installation.
What are the shipping and warranty terms?
Typical international transit is 5–15 days, with standard shipping generally free. Expedited options may be available at checkout. The kit is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the applicable standard return period when the item is unused and in its original condition.
Safety and Important Information
- Verify the engine model, serial number, temperature rating, and original-part details before ordering.
- Do not open the cooling system while the engine is hot or pressurized.
- Use the correct coolant, sealing method, and fastener torque specified by the engine service manual.
- This is an aftermarket replacement, not an OEM Mercury/MerCruiser component.
- Professional installation is recommended when the required service procedures are unfamiliar.
About Sea Sierra
- Pro-Grade Standards — Marine replacement parts selected for dependable service in real-world conditions.
- Fast Global Fulfillment — Standard delivery is available to most regions, with typical transit of 5–15 days.
- Manufacturer-Direct Value — Competitive pricing with attention to materials and quality control.
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