140°F Thermostat Kit – Fits OMC Cobra, Volvo Penta 7.4L-8.2L (Replaces 3853983, 18-3676)
140°F Thermostat Kit – Fits OMC Cobra, Volvo Penta 7.4L-8.2L (Replaces 3853983, 18-3676) is backordered and will ship as soon as it is back in stock.
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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-8.2L (Repla...
Product Details
This marine 140°F Thermostat Kit – Fits OMC Cobra/Volvo Penta 7.4L-8.2L V6/V8 is engineered for specific OMC Cobra and Volvo Penta sterndrive engines. It ensures a consistent 140°F (60°C) operating temperature for 7.4L (1994–1998) and 8.2L (1998) OMC models, plus all 7.4L and 8.2L Volvo Penta engines from 1993 forward.
It serves as a direct replacement for multiple OEM and aftermarket parts, including OMC 3853983, Volvo Penta 3853983, and Sierra 18-3676.
- Engine-mounted for straightforward installation.
- Maintains a factory-specified 140°F (60°C) engine temperature for optimal performance.
- Includes thermostat, O-ring, and gasket for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| OMC Stern Drive | 3853983 |
| OMC Stern Drive | 312797 |
| OMC Stern Drive | 307239 |
| Volvo Penta | 3853983 |
| Volvo Penta | 3852071 |
| Volvo Penta | 835417 |
| Sierra | 18-3676 |
| Mallory | 9-43026 |
| QuickMarine | 18-3676 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For OMC Cobra Owners: This kit fits 7.4L models from 1994–1998 and the 8.2L model for the 1998 model year.
For Volvo Penta Owners: This kit is compatible with all 7.4L and 8.2L models manufactured from 1993 to present.
| Brand | Model | Years | OEM Part No. |
|---|---|---|---|
| OMC | 7.4L | 1994–1998 | 3853983 |
| OMC | 8.2L | 1998 | 3853983 |
| Volvo Penta | 7.4L (all models) | 1993–Current | 3853983 |
| Volvo Penta | 8.2L (all models) | 1993–Current | 3853983 |
Technical Specs
- Product Type
- Marine Engine Thermostat Kit
- Installation
- Engine Mount
- Temperature Rating
- 140°F (60°C)
- Application
- OMC 7.4L, 8.2L V6/V8; Volvo Penta 7.4L, 8.2L V6/V8
- Housing Material
- Marine Grade Thermostat Assembly
- Weight
- 2.82 oz (0.08 kg)
- Other Technical Attributes
- Cooling Engine Function
What’s in the Box
- 1 x Thermostat (3853983)
- 1 x O-Ring (3852071/18-7170)
- 1 x Thermostat Gasket (835417/18-0398)
Installation Notes
- Disconnect the battery and allow the engine to cool completely before starting.
- Drain the engine coolant into a suitable, clean container.
- Locate the thermostat housing on the engine and carefully remove the retaining bolts.
- Remove the old thermostat, gasket, and O-ring. Note the thermostat's orientation before removal.
- Thoroughly clean the mating surfaces of the housing and the engine block to ensure a proper seal.
- Install the new thermostat in the correct orientation, followed by the new gasket and O-ring.
- Reinstall the thermostat housing and tighten the bolts to the manufacturer's recommended torque specifications.
- Refill the cooling system, check for leaks, and start the engine to verify proper operation and temperature control.
Troubleshooting & FAQ
How do I confirm this thermostat fits my specific engine model?
First, check your existing part for any of the numbers listed in our Part Number Matrix. Second, verify your engine brand, model, and year against the compatibility tables. If your model is listed, it is a confirmed fit.
Is this a 140°F or a different temperature thermostat?
This is a 140°F (60°C) thermostat kit. Always confirm your engine manufacturer's recommended operating temperature before installation, as using the wrong temperature can affect performance and engine health.
What are the signs of a failing marine thermostat?
Common symptoms include engine overheating, the engine running too cold and not reaching operating temperature, erratic readings on the temperature gauge, or coolant leaks from the thermostat housing area.
How often should a marine thermostat be replaced?
As a preventative maintenance item, it is wise to inspect your thermostat annually and replace it every 2-3 years or 200-300 operating hours, even if it has not failed, to ensure reliable engine cooling.
What is the difference between an OEM and an aftermarket part?
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.
How fast is shipping and what does it cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
What is the warranty and return policy?
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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