140°F Thermostat Kit – Fits MerCruiser V8 Engines 1982 & Older (Replaces 807252Q3)
140°F Thermostat Kit – Fits MerCruiser V8 Engines 1982 & Older (Replaces 807252Q3) 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
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140°F Thermostat Kit – Fits MerCruiser V8 Engines 1982 & Older ...
Product Details
This 140°F Thermostat Kit – Fits MerCruiser V8 Engines 1982 & Older is designed for 1982 and older MerCruiser V8 marinized sterndrive and inboard engines (Ford or General Motors) with standard cooling systems. It is also compatible with 1996 and older high-performance MerCruiser V8 engines.
This kit serves as a direct interchange for Mercury/Quicksilver 807252Q3, Sierra 18-3646, A.A 23-47508T, and NETYANPI 8M0089715.
- Engineered for direct-fit, OEM-equivalent installation.
- Includes thermostat, a full set of gaskets, and a brass sleeve for a complete service.
- Maintains a consistent 140°F (60°C) operating temperature.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/Quicksilver | 807252Q3 |
| Sierra | 18-3646 |
| A.A | 23-47508T |
| NETYANPI | 8M0089715 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This thermostat fits a range of V8 engines manufactured by Ford and General Motors for MerCruiser, covering both standard and high-performance models up to specific years. Please check your application carefully.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | V8 GM engines | Various | 4-Stroke | Up to 1982 | 807252Q3 | Standard cooling systems |
| MerCruiser | V8 Ford engines | Various | 4-Stroke | Up to 1982 | 807252Q3 | Standard cooling systems |
| MerCruiser | High-performance V8 GM engines | Various | 4-Stroke | Up to 1996 | 807252Q3 | With closed cooling systems |
| MerCruiser | High-performance V8 Ford engines | Various | 4-Stroke | Up to 1996 | 807252Q3 | With closed cooling systems |
Technical Specs
- Product Type
- Thermostat Kit
- Installation
- Direct replacement
- Temperature Rating
- 140°F (60°C)
- Connection
- OEM replacement
- Dimensions
- L: 1.5 in, W: 7.25 in, H: 6.0 in
- Weight
- 0.1 kg (0.22 lb)
- Fitting Type
- Standard OEM fit
- Operating Temperature
- 140°F (60°C)
- Other Technical Attributes
- For use with standard cooling systems
What’s in the Box
- 1 x 140°F Thermostat
- 5 x Gaskets (including flat and rubber gaskets)
- 1 x Brass Sleeve
Installation Notes
- Disconnect the battery and allow the engine to cool completely before starting.
- Drain the engine coolant to a level below the thermostat housing.
- Locate and remove the thermostat housing, noting the orientation of the old thermostat.
- Clean the mating surfaces of the housing and engine block thoroughly.
- Insert the new thermostat, ensuring it is correctly oriented (usually with the spring side facing the engine block).
- Place the new gasket that matches your housing onto the engine block.
- Reinstall the thermostat housing and tighten the bolts to the manufacturer's specified torque.
- Refill the cooling system with the appropriate coolant mix and volume.
- Reconnect the battery, start the engine, let it warm up, and check carefully for any leaks.
Troubleshooting & FAQ
Is this a 140°F or 160°F thermostat?
This is a 140°F (60°C) thermostat kit. While the OEM part number 807252Q3 may be associated with different temperature ratings in some contexts, this specific aftermarket kit is rated for 140°F to match the requirements of the specified older and high-performance engines.
How do I know if this thermostat kit fits my engine?
This kit is designed for MerCruiser V8 engines (GM and Ford builds) from 1982 and earlier, as well as high-performance models up to 1996. Please consult the "Engine & Model Compatibility" table and cross-reference your OEM part number to ensure a correct match.
What are the signs of a failing thermostat?
Common symptoms include engine overheating, running too cold (not reaching operating temperature), erratic temperature gauge readings, and coolant leaks from the thermostat housing area.
When should I replace my engine's thermostat?
Thermostats are a vital maintenance item. It's recommended to replace them every few hundred hours of operation, as part of any major cooling system service, or immediately if you suspect failure.
Why are there multiple gaskets in the kit?
The kit includes a variety of gaskets to fit different thermostat housing configurations found across the range of compatible engines. You will only use the single gasket that perfectly matches your specific housing.
Is this for standard or closed cooling systems?
It is primarily for standard (raw water) cooling systems but is also listed as compatible with certain high-performance models that may use closed cooling. Always verify your specific engine's cooling system requirements.
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.
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