Thermostat Kit – Fits Volvo Penta 4.3L-8.2L, OMC Cobra 4.3L-5.8L (Replaces 0769578, 3853983, 3852111, 0986506)
Thermostat Kit – Fits Volvo Penta 4.3L-8.2L, OMC Cobra 4.3L-5.8L (Replaces 0769578, 3853983, 3852111, 0986506) 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.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat Kit – Fits Volvo Penta 4.3L-8.2L, OMC Cobra 4.3L-5.8L (R...
Product Details
This Thermostat Kit – Fits Volvo Penta 4.3L, 5.0L, 5.7L, 7.4L, 8.1L is designed for a wide range of gasoline marine engines. It is compatible with Volvo Penta 4.3L, 5.0L, 5.7L V6 and 7.4L, 8.1L, 8.2L V8 models from 1994 to current, as well as OMC Cobra 4.3L, 5.0L, 5.7L, and 5.8L engines from 1994–1998.
It serves as a direct replacement for Volvo Penta part numbers 0769578 and 3853983; OMC 0986506 and 3853983; and Sierra 18-3676.
- Installs as a direct OEM-equivalent replacement.
- Rated for a 60°C (140°F) opening temperature.
- Includes the thermostat, gasket, and O-ring needed for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Volvo Penta | 0769578 / 3853983 |
| OMC | 0986506 / 3853983 |
| Sierra | 18-3676 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Volvo Penta engines, this kit fits V6 and V8 models from 1994 to current, including Big Block and Drive series.
For OMC engines, this kit is compatible with Cobra Stern Drive models from 1994–1998 and select earlier models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Volvo Penta | 7.4-BY, 7.4-EF, 7.4-LK, 7.4-WT | 7.4L | 4-Stroke | 1993–2000 | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 7.4Gi-BY, 7.4Gi-EF, 7.4Gi-HU, 7.4Gi-LK, 7.4Gi-NC, 7.4Gi-WT, 7.4GiPEFS | 7.4L | 4-Stroke | 1993–2000 | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 7.4GL-BY, 7.4GL-HU, 7.4GL-LK, 7.4GL-MD, 7.4GL-NC | 7.4L | 4-Stroke | 1993–2000 | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 7.4GSi-BY, 7.4GSi-EF, 7.4GSi-HU, 7.4GSi-LK, 7.4GSi-NC, 7.4GSi-WT, 7.4GSiPEFS | 7.4L | 4-Stroke | 1993–2000 | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 8.1Gi-A to 8.1Gi-J | 8.1L | 4-Stroke | 2000–Current | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 8.1GiC-400-J/Q, 8.1GiCE-400-J/M/P/Q | 8.1L | 4-Stroke | 2000–Current | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 8.1GiE-J/K/M/P, 8.1Gii-A to H | 8.1L | 4-Stroke | 2000–Current | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 8.1GSi-A, 8.1GSii-A | 8.1L | 4-Stroke | 2000–Current | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 8.1GXi-A to J, 8.1GXiE-J/K/M/P | 8.1L | 4-Stroke | 2000–Current | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 8.1GXii-A to G | 8.1L | 4-Stroke | 2000–Current | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 8.1OSi-A to D/J, 8.1OSiE-J | 8.1L | 4-Stroke | 2000–Current | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | 8.2Gi-EF/WT, 8.2GL-HU/MD, 8.2GSi-BY/EF/LK/NC/WT | 8.2L | 4-Stroke | 1993–2000 | 0769578/3853983 | Big Block V8 Series |
| Volvo Penta | DPX375-A/B/BF, DPX385/XEFS, DPX415/XEFS, DPX420-A/B/F | N/A | 4-Stroke | 1994–2000 | 0769578/3853983 | Drive Models |
| Volvo Penta | 4.3L (All Models) | 4.3L | 4-Stroke | 1994–Current | 0769578/3853983 | V6 Series |
| Volvo Penta | 5.0L (All Models) | 5.0L | 4-Stroke | 1994–Current | 0769578/3853983 | V8 Series |
| Volvo Penta | 5.7L (All Models Except OSi) | 5.7L | 4-Stroke | 1994–Current | 0769578/3853983 | V8 Series |
| OMC | Cobra 4.3L | 4.3L | 4-Stroke | 1994–1998 | 0986506/3853983 | Stern Drive |
| OMC | Cobra 5.0L | 5.0L | 4-Stroke | 1994–1998 | 0986506/3853983 | Stern Drive |
| OMC | Cobra 5.7L | 5.7L | 4-Stroke | 1994–1998 | 0986506/3853983 | Stern Drive |
| OMC | Cobra 5.8L | 5.8L | 4-Stroke | 1994–1998 | 0986506/3853983 | Stern Drive |
| OMC | Cobra | 80-200 HP | 4-Stroke | 1968–1969 | 0986506/3853983 | Stern Drive |
Technical Specs
- Product Type
- Thermostat Kit
- Installation
- Direct OEM replacement
- Temperature Rating
- 60°C / 140°F
- Fuel Type
- Gasoline
- Operating Temperature
- 60°C (140°F) opening temperature
- Cooling System
- Closed cooling system compatibility
- Warranty
- Varies by manufacturer (typically 1 year)
What’s in the Box
- 1 x Thermostat (3853983)
- 1 x Gasket (3852111)
- 1 x O-ring (3852071)
Installation Notes
- Disconnect the vessel's battery before beginning work.
- Drain coolant from the engine block to a level below the thermostat housing.
- Loosen the hose clamp and carefully remove the main coolant hose from the housing cover.
- Remove the bolts securing the thermostat housing cover to the engine.
- Lift the cover and remove the old thermostat and gasket or O-ring. Note the thermostat's orientation.
- Thoroughly clean the mating surfaces of the housing and engine block to ensure a proper seal.
- Install the new thermostat in the correct orientation.
- Place the new gasket or O-ring into position on the housing.
- Re-secure the housing cover and tighten the bolts to the manufacturer's specified torque.
- Reattach the coolant hose and tighten the hose clamp.
- Refill the cooling system with the manufacturer-recommended coolant.
- Reconnect the battery, start the engine, and carefully inspect for any leaks as the engine warms up.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs include the engine overheating, running too cool (not reaching operating temperature), erratic temperature gauge readings, or visible coolant leaks around the thermostat housing.
What is the significance of the 140°F (60°C) temperature?
This thermostat begins to open at 140°F (60°C). This temperature is standard for many raw-water cooled marine engines to ensure efficient operation while preventing salt and mineral buildup that can occur at higher temperatures.
Is everything I need for the swap included?
Yes, this kit includes the thermostat, a flat gasket, and an O-ring. This covers the typical sealing components required for the listed Volvo Penta and OMC models.
Can a bad thermostat cause poor engine performance?
Absolutely. If a thermostat is stuck open, the engine may not reach its proper operating temperature, leading to increased fuel consumption and carbon buildup. If it's stuck closed, the engine will quickly overheat, risking severe damage.
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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