Thermostat Kit – Fits OMC Cobra & Volvo Penta (Replaces 3853799, 982554)
Thermostat Kit – Fits OMC Cobra & Volvo Penta (Replaces 3853799, 982554) is backordered and will ship as soon as it is back in stock.
Couldn't load pickup availability
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
Thermostat Kit – Fits OMC Cobra & Volvo Penta (Replaces 3853799...
Product Details
This Marine Thermostat Kit – Fits OMC Cobra 120/140HP & Volvo Penta 2.5L/3.0L (Replaces 3853799, 982554) is designed for reliable temperature regulation in OMC 2.5L and 3.0L sterndrive engines from 1968 and newer, and Volvo Penta 3.0L sterndrive engines from 1996 and newer. It ensures your engine operates at the correct temperature for optimal performance and fuel efficiency.
This kit serves as a direct interchange for Sierra 18-3670, Sierra 18-3621, SeaSierra 3853799, QuickMarine 3853799, and GLM 13440.
- Installs as a direct replacement for the original thermostat and gaskets.
- Maintains a consistent engine operating temperature of 160°F (71°C).
- Includes the thermostat and all necessary gaskets for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Sierra | 18-3670 |
| Sierra | 18-3621 |
| SeaSierra | 3853799 |
| QuickMarine | 3853799 |
| GLM | 13440 |
| OMC/Volvo Penta | 3853799 |
| OMC/Volvo Penta | 982554 |
Engine & Model Compatibility
Confirm your engine model and year in the tables below.
Fits OMC Cobra sterndrive engines (1968 and newer) with 2.5L and 3.0L configurations.
| Brand | Model | Rated HP | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| OMC | Cobra | 120 | 1968 and Up | 3853799/982554 | With 2.5L engines |
| OMC | Cobra | 140 | 1968 and Up | 3853799/982554 | With 3.0L engines |
Fits Volvo Penta 3.0L sterndrive applications from 1996 and up.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| Volvo Penta | 3.0L | 1996 and Up | 3853799/982554 | Sterndrive applications |
Technical Specs
- Product Type
- Thermostat Kit with Gaskets
- Installation
- Direct replacement
- Temperature Rating
- 160°F (71°C)
- Application
- Marine cooling system
- Operating Temperature
- 160°F (71°C) opening temperature
What’s in the Box
- 1 x Thermostat (3853799)
- 1 x Thermostat Housing Gasket (0314809)
- 1 x Thermostat Gasket (0313416)
Installation Notes
- Ensure the engine is completely cool before beginning work.
- Disconnect the battery to prevent any accidental starts.
- Locate the thermostat housing on the engine. Place a drain pan underneath to catch any spilled coolant.
- Loosen and remove the bolts securing the thermostat housing cover.
- Carefully remove the old thermostat and discard it. Note its orientation.
- Clean both the housing and cover surfaces, removing all traces of the old gasket material.
- Install the new thermostat in the correct orientation, followed by the new gaskets.
- Reattach the housing cover and tighten the bolts to the manufacturer's specified torque.
- Reconnect the battery, refill the cooling system, and check for leaks after starting the engine.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs of a failing thermostat include engine overheating, engine temperature running lower than normal, or erratic temperature gauge readings. A thermostat stuck open will prevent the engine from reaching its optimal operating temperature, while one stuck closed will cause it to overheat.
Will this fit my specific boat model?
This kit is designed for the engine series listed, not specific boat models. Please verify compatibility using the OMC and Volvo Penta engine models and years provided in the tables above. Cross-reference the part numbers to ensure a match.
Is this a 160°F or 140°F thermostat?
This is a 160°F (71°C) thermostat kit. It is critical to use the temperature rating specified for your engine to ensure correct performance and avoid potential damage.
What is the recommended replacement interval?
Marine thermostats should be inspected annually and replaced every 2-3 years as part of regular preventative maintenance, or immediately if you notice signs of failure. Saltwater environments may require more frequent replacement.
What’s the difference between OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It has been built to meet or exceed OEM-level specifications with comparable materials. Our parts are manufactured in an ISO 9002 facility and are batch-inspected for quality and consistency.
What are the shipping speed & costs?
We ship worldwide quickly—typical transit time is 5–15 days for most regions. Standard shipping is free, with expedited options available at checkout where applicable.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their original condition. See our 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, 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.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
