140°F Marine Engine Thermostat Kit – Fits OMC Cobra and Volvo Penta 7.4L, 8.1L and 8.2L V6/V8 Engines
140°F Marine Engine Thermostat Kit – Fits OMC Cobra and Volvo Penta 7.4L, 8.1L and 8.2L V6/V8 Engines is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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140°F Marine Engine Thermostat Kit – Fits OMC Cobra and Volvo Penta...
140°F Marine Engine Thermostat Kit – Fits OMC Cobra and Volvo Penta 7.4L, 8.1L and 8.2L V6/V8 Engines is backordered and will ship as soon as it is back in stock.
Product Details
This 140°F marine engine thermostat kit is intended for selected OMC Cobra and Volvo Penta stern-drive applications using 7.4L, 8.1L and 8.2L V6/V8 gasoline engines. The 140°F (60°C) thermostat helps the engine maintain its specified operating temperature in freshwater- and saltwater-cooled marine applications.
The kit is listed as a replacement reference for OMC part numbers 3853983, 312797 and 307239; Volvo Penta part numbers 3853983, 3852071 and 835417; Sierra 18-3676; and Mallory 9-43026. Always compare the required part number, engine model and existing component before installation.
- Installation Method: Direct engine-mounted installation.
- Operating Environment: Suitable for freshwater- and saltwater-cooled engines.
- Kit Contents: Thermostat, thermostat gasket and O-ring.
- Thermostat Rating: 140°F (60°C).
Part Number Matrix
Use these references to help compare OEM and aftermarket replacement numbers. Part-number references do not replace confirmation of the exact engine application.
| 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
The application references below summarize the listed OMC Cobra and Volvo Penta engine families. Model-year and serial-number changes may affect fitment, so verify the original thermostat and required part number before ordering.
| Brand | Engine Family | Rated HP | Stroke | Listed Years | OEM Reference |
|---|---|---|---|---|---|
| OMC Cobra | 7.4L V8 | Various | 4-Stroke | 1994–1998 | 3853983 |
| OMC Cobra | 8.2L V8 | Various | 4-Stroke | 1998 | 3853983 |
| Brand | Engine Family | Rated HP | Stroke | Listed Years | OEM Reference |
|---|---|---|---|---|---|
| Volvo Penta | 7.4L | Various | 4-Stroke | 1993–current | 3853983 |
| Volvo Penta | 8.1L | Various | 4-Stroke | Verify by model and serial number | 3853983 |
| Volvo Penta | 8.2L | Various | 4-Stroke | 1993–current | 3853983 |
Technical Specs
- Product Type
- Marine engine thermostat kit
- Installation
- Engine mounted
- Engine Type
- Gasoline marine engines
- Connection
- Direct engine mount
- Temperature Rating
- 140°F (60°C)
- Cooling Applications
- Freshwater- and saltwater-cooled engines
What’s in the Box
- 1 × 140°F thermostat
- 1 × thermostat gasket
- 1 × O-ring
The included components are supplied together as a replacement kit. The component reference numbers commonly associated with the kit are thermostat 3853983 and 09886506, gasket 835417 and 18-0398, and O-ring 3852071 and 18-7170.
Installation Notes
- Ensure the engine is cool before beginning work. Drain coolant or raw water as required by the engine's cooling-system design.
- Locate the thermostat housing on the engine.
- Remove the housing fasteners carefully and lift the housing to access the existing thermostat.
- Remove the old thermostat and gasket. Clean the mating surfaces of old gasket material, scale and corrosion.
- Install the new thermostat, O-ring and gasket in the correct orientation.
- Reinstall the thermostat housing and tighten the fasteners to the engine manufacturer's specified torque.
- Refill or reconnect the cooling system according to the engine service procedure.
- Run the engine, bring it to operating temperature and check the housing for leaks. Correct the coolant level or raw-water flow as necessary.
Troubleshooting & FAQ
How do I know if my thermostat has failed?
Possible symptoms include overheating, an engine that runs below its normal temperature, or large temperature fluctuations. A thermostat stuck open may prevent the engine from reaching operating temperature, while one stuck closed may cause overheating.
What is the difference between a 140°F and a 160°F thermostat?
The temperature rating indicates the approximate temperature at which the thermostat begins to open. A 140°F thermostat is commonly used in raw-water-cooled marine applications, while some closed-cooling systems use a higher-rated thermostat. Use the temperature specified for the exact engine model.
My engine model is listed, but my old part looks different. What should I do?
Do not install the part until the difference is resolved. Marine manufacturers may change components during a model year. Compare the part number, dimensions and housing arrangement with the existing component and verify the engine model and serial number.
Is this thermostat compatible with V6 engines?
The replacement references may appear in V6 and V8 application data, but the available application information does not provide a complete V6 model-by-model list. Verify the required part number for the specific V6 engine and year before purchasing.
Is this an OEM part?
This is an aftermarket replacement kit, not an OEM component. The listed OEM and aftermarket numbers are provided as application references only.
What are the shipping speeds and costs?
Shipping methods, delivery estimates and applicable costs are shown at checkout and depend on the destination and selected service.
What is the warranty and return policy?
Warranty coverage and return eligibility are governed by the current store policies. Contact support with your order details before returning or installing a suspected defective part.
Safety & Important Information
- Verify the engine model, year, serial number and required thermostat temperature before ordering.
- Compare the replacement part and housing arrangement with the existing component before installation.
- Allow the engine to cool fully before opening the thermostat housing or cooling system.
- Follow the engine manufacturer's service procedure and specified fastener torque.
- This is an aftermarket replacement part, not an OEM component.
- Professional installation is recommended when the correct application or cooling-system procedure is uncertain.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for demanding real-world operating conditions.
- Global Fulfillment — Shipping options and delivery estimates are provided during checkout based on destination.
- Manufacturer-Direct Value — We work with manufacturing partners to provide replacement parts at competitive prices.
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