140°F Thermostat Kit – Fits OMC Cobra/Volvo Penta 7.4L/8.1L/8.2L (Replaces 3853983, 312797, 307239)
140°F Thermostat Kit – Fits OMC Cobra/Volvo Penta 7.4L/8.1L/8.2L (Replaces 3853983, 312797, 307239) 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.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
140°F Thermostat Kit – Fits OMC Cobra/Volvo Penta 7.4L/8.1L/8.2L (R...
Product Details
This 140°F Thermostat Kit – Fits OMC Cobra/Volvo Penta 7.4L/8.1L/8.2L V6/V8 is designed for OMC Cobra and Volvo Penta stern drives with 7.4L, 8.1L, and 8.2L engines (1993–current). It ensures your engine maintains the correct operating temperature of 140°F (60°C) for optimal performance and longevity in both freshwater and saltwater environments.
This kit serves as a direct replacement for OMC part numbers 3853983, 312797, and 307239; Volvo Penta 3853983, 3852071, and 835417; Sierra 18-3676; and Mallory 9-43026.
- Installation Method: Direct engine-mounted installation.
- Operating Environment: Suitable for both freshwater and saltwater cooled engines.
- Complete Kit: Includes the thermostat, gasket, and O-ring needed for a full replacement.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| OMC | 3853983 |
| OMC | 312797 |
| OMC | 307239 |
| Volvo Penta | 3853983 |
| Volvo Penta | 3852071 |
| Volvo Penta | 835417 |
| Sierra | 18-3676 |
| Mallory | 9-43026 |
Engine & Model Compatibility
Confirm your engine model and year in the tables below.
This thermostat kit is confirmed to fit specific OMC Cobra and Volvo Penta V8 engines as detailed below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| OMC | 7.4L | All | 4-Stroke | 1994–1998 | 3853983 |
| OMC | 8.2L | All | 4-Stroke | 1998 | 3853983 |
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Volvo Penta | 7.4L (all models) | Various | 4-Stroke | 1993–current | 3853983 |
| Volvo Penta | 8.2L (all models) | Various | 4-Stroke | 1993–current | 3853983 |
Technical Specs
- Product Type
- Marine Engine Thermostat Kit
- Installation
- Engine Mounted
- Fuel Type
- Gasoline
- Connection
- Direct Engine Mount
- Housing Material
- Marine Grade Material
- Temperature Rating
- 140°F (60°C)
- Operating Temperature
- 140°F (60°C)
- Other Technical Attributes
- For fresh water and salt water cooled engines
What’s in the Box
- 1 x Thermostat (Replaces 3853983, 09886506)
- 1 x Thermostat Gasket (Replaces 835417, 18-0398)
- 1 x O-Ring (Replaces 3852071, 18-7170)
Installation Notes
- Ensure the engine is cool. Drain the engine coolant into a suitable container.
- Locate the thermostat housing on the engine block.
- Carefully remove the bolts and lift the housing to access the old thermostat.
- Remove the old thermostat and gasket. Thoroughly clean both mating surfaces of any old gasket material or corrosion.
- Install the new thermostat, O-ring, and gasket in the correct orientation.
- Re-secure the thermostat housing, tightening the bolts to the manufacturer's specified torque.
- Refill the cooling system with the appropriate coolant.
- Start the engine and let it warm up, checking for any leaks around the housing. Top off coolant as needed.
Troubleshooting & FAQ
How do I know if my thermostat has failed?
Common signs of a failed thermostat include engine overheating, engine temperature that is too low, or large fluctuations in the temperature gauge. A thermostat stuck open will prevent the engine from reaching its proper operating temperature, while one stuck closed will cause overheating.
What is the difference between a 140°F and a 160°F thermostat?
The temperature rating indicates when the thermostat opens. A 140°F thermostat is typically used in raw water (salt or fresh) cooled engines to reduce salt and mineral buildup. A 160°F thermostat is common for closed (antifreeze) cooling systems, allowing the engine to run slightly warmer for better efficiency. Always use the temperature specified for your engine model.
My engine model is listed, but my old part looks different. What should I do?
Do not install the part. Manufacturers sometimes make mid-year changes. Always compare our photos and specifications to your existing part before installation. If there are discrepancies, please contact us for assistance.
Is this thermostat compatible with V6 engines?
While the OEM part number is cross-referenced for some OMC and Volvo Penta V6 models, we do not have a detailed application list for them. Please verify the part number required for your specific V6 engine model and year before purchasing.
Is this an OEM part?
This is a high-quality aftermarket replacement, not an OEM component. It is engineered to meet or exceed OEM specifications for fit, form, and function and is produced in an ISO 9002 certified facility to ensure quality and reliability.
What are your shipping speeds and costs?
We ship worldwide quickly—typical transit is 5–15 days for most locations. Standard shipping is free. Expedited shipping options and exact costs are available at checkout, depending on your destination.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter an issue, contact our support team with your order details. Returns are accepted within our standard window for parts that are unused and in their original condition. Please see our full policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement part, not an OEM component.
- Professional installation is recommended for safety and optimal performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without ever compromising on materials or quality control.
Payment & Security
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