Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8 (Replaces 383307, 18-3653, 3856961)
Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8 (Replaces 383307, 18-3653, 3856961) is backordered and will ship as soon as it is back in stock.
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Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8 (...
Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8 (Replaces 383307, 18-3653, 3856961) is backordered and will ship as soon as it is back in stock.
Product Details
This Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8 (Replaces 383307, 18-3653, 3856961) is a 160°F thermostat kit designed for a wide range of OMC Cobra and Volvo Penta sterndrive applications. It is engineered for V6 and V8 engines from 3.8L to 7.5L, covering models manufactured from the 1970s through the 1990s.
This kit serves as a direct replacement for OMC part numbers 379754, 383307, and 3856961; Sierra 18-3653 and 18-3554; GLM 13430 and 13060; Mallory 9-43156 and 9-43021; and Volvo Penta 3856961.
- Engineered for direct replacement installation.
- Maintains a 160°F (71°C) operating temperature for optimal engine performance.
- Includes necessary gaskets and an O-ring for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| OMC | 379754 |
| OMC | 383307 |
| OMC | 3856961 |
| Sierra | 18-3653 |
| Sierra | 18-3554 |
| GLM | 13430 |
| GLM | 13060 |
| Mallory | 9-43156 |
| Mallory | 9-43021 |
| Volvo Penta | 3856961 |
Engine & Model Compatibility
Confirm your engine model and year in the tables below to ensure proper fitment.
For OMC Cobra sterndrives, this kit is compatible with various models from 90 HP up to 7.5L engines, spanning from the 1970s through the 1990s.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| OMC | 90 | 90 HP | 4-Stroke | 1970 | 379754/383307 | |
| OMC | 100 | 100 HP | 4-Stroke | 1972–1973 | 379754/383307 | |
| OMC | 120 | 120 HP | 4-Stroke | 1969–1980 | 379754/383307 | |
| OMC | 140 | 140 HP | 4-Stroke | 1973–1980 | 379754/383307 | |
| OMC | 155 | 155 HP | 4-Stroke | 1969–1972 | 379754/383307 | |
| OMC | 165 | 165 HP | 4-Stroke | 1972–1976 | 379754/383307 | |
| OMC | 170 | 170 HP | 4-Stroke | 1974 | 379754/383307 | |
| OMC | 175 | 175 HP | 4-Stroke | 1975–1977 | 379754/383307 | |
| OMC | 185 | 185 HP | 4-Stroke | 1978–1980 | 379754/383307 | |
| OMC | 190 | 190 HP | 4-Stroke | 1974–1977 | 379754/383307 | |
| OMC | 200 | 200 HP | 4-Stroke | 1979–1981 | 379754/383307 | |
| OMC | 210 | 210 HP | 4-Stroke | 1969–1972 | 379754/383307 | |
| OMC | 215 | 215 HP | 4-Stroke | 1971 | 379754/383307 | |
| OMC | 225 | 225 HP | 4-Stroke | 1971 | 379754/383307 | |
| OMC | 230 | 230 HP | 4-Stroke | 1979–1981 | 379754/383307 | |
| OMC | 235 | 235 HP | 4-Stroke | 1971, 1975–1977 | 379754/383307 | |
| OMC | 240 | 240 HP | 4-Stroke | 1978 | 379754/383307 | |
| OMC | 245 | 245 HP | 4-Stroke | 1972–1975 | 379754/383307 | |
| OMC | 250 | 250 HP | 4-Stroke | 1970–1973, 1979 | 379754/383307 | |
| OMC | 260 | 260 HP | 4-Stroke | 1979–1981 | 379754/383307 | |
| OMC | 305 | 305 HP | 4-Stroke | 1977–1982 | 379754/383307 | |
| OMC | 350 | 350 HP | 4-Stroke | 1977–1982 | 379754/383307 | |
| OMC | 454 | 454 HP | 4-Stroke | 1977–1982 | 379754/383307 | |
| OMC | 3.8L | 3.8L | 4-Stroke | 1981–1985 | 383307 | |
| OMC | 4.3L | 4.3L | 4-Stroke | 1985–1986 | 383307 | |
| OMC | 4.3L | 4.3L | 4-Stroke | 1994–1997 | 3856961 | 4.3L and 4.3HO |
| OMC | 5.0L | 5.0L | 4-Stroke | 1982–1988, 1994–1997 | 383307/3856961 | |
| OMC | 5.7L | 5.7L | 4-Stroke | 1982–1988, 1994–1997 | 383307/3856961 | |
| OMC | 5.8L | 5.8L | 4-Stroke | 1994–1997 | 3856961 | Includes 5.8EFI |
| OMC | 7.5L | 7.5L | 4-Stroke | 1982–1988 | 383307 |
For Volvo Penta engines, this kit fits specific GL, GS, Gi, FL, Fi, and FSi series models—verify your part number (3856961).
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Volvo Penta | 4.3GL | 4.3L | 4-Stroke | 3856961 | |
| Volvo Penta | 4.3GS | 4.3L | 4-Stroke | 3856961 | |
| Volvo Penta | 4.3Gi | 4.3L | 4-Stroke | 3856961 | |
| Volvo Penta | 5.0FL | 5.0L | 4-Stroke | 3856961 | |
| Volvo Penta | 5.0Fi | 5.0L | 4-Stroke | 3856961 | |
| Volvo Penta | 5.7GL | 5.7L | 4-Stroke | 3856961 | |
| Volvo Penta | 5.7Gi | 5.7L | 4-Stroke | 3856961 | |
| Volvo Penta | 5.8FL | 5.8L | 4-Stroke | 3856961 | |
| Volvo Penta | 5.8Fi | 5.8L | 4-Stroke | 3856961 | |
| Volvo Penta | 5.8FSi | 5.8L | 4-Stroke | 3856961 |
Technical Specs
- Product Type
- Marine Engine Thermostat Kit
- Installation
- Direct Replacement
- Temperature Rating
- 160°F (71°C)
- Connection
- O-ring Seal
- Housing Material
- Brass/Bronze
- Operating Temperature
- 160°F (71°C) Opening Temperature
- Warranty
- Standard Manufacturer Warranty
- Other Technical Attributes
- Includes gaskets and O-ring for complete installation
What’s in the Box
- 1 x 160°F Thermostat (Replaces OMC 3856961)
- 1 x Thermostat Housing Gasket (Replaces OMC 3852111)
- 1 x O-ring (Replaces OMC 3852071)
- 1 x Gasket (Replaces OMC 314809)
- 1 x Gasket (Replaces OMC 313416)
Installation Notes
- Ensure the engine is completely cool and disconnect the battery terminals for safety.
- Drain the engine coolant to a level below the thermostat housing.
- Loosen the hose clamps and remove the coolant hoses connected to the thermostat housing.
- Unbolt and remove the thermostat housing cover. Note the orientation of the old thermostat.
- Remove the old thermostat and discard the old gaskets and O-ring.
- Thoroughly clean all mating surfaces of the housing and engine block to remove old gasket material and corrosion.
- Place the new thermostat into the housing in the correct orientation.
- Install the new gaskets and O-ring as required for your specific model.
- Reinstall the housing cover and torque the bolts to the manufacturer's specified value.
- Reconnect hoses, refill the cooling system with the appropriate coolant, and reconnect the battery.
- Start the engine and let it warm up, checking carefully for any leaks around the housing.
Troubleshooting & FAQ
How do I know if my engine thermostat is failing?
Common signs of a faulty thermostat include the engine overheating on gauges, or conversely, running too cool and not reaching its proper operating temperature. You might also notice coolant leaks around the thermostat housing.
Is a 160°F rating correct for my marine engine?
Yes, a 160°F (71°C) thermostat is the standard temperature rating for most raw-water cooled sterndrive and inboard marine engines like those listed. It provides the right balance for efficient combustion and prevents salt and mineral crystallization.
Why does this kit have 5 pieces while others only have 3?
This comprehensive kit includes two additional gaskets (OMC 314809 and 313416) to cover a wider variety of OMC and Volvo Penta housing designs over the years. You will only use the thermostat, O-ring, and the specific housing gasket that matches your engine's configuration.
Do I need to use a sealant on the gaskets?
Generally, new gaskets are designed to seal without additional sealant. However, a light, non-hardening sealant approved for marine use can be applied to damaged or pitted surfaces to ensure a leak-proof seal. Always consult your engine's service manual for specific recommendations.
What is the difference between an OEM and an aftermarket part?
This listing is for a high-quality aftermarket replacement part, not an original equipment manufacturer (OEM) component. It has been engineered to meet or exceed OEM specifications using comparable materials. Our parts are made in an ISO 9002 certified facility and are batch-inspected to ensure quality and consistency.
How fast do you ship and what does it cost?
p> We ship worldwide quickly. Typical transit time is 5–15 days for most regions. Standard shipping is free, and expedited shipping options, where available, will be presented at checkout.What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal operating use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard return window for unused items in their original condition. See our full policy page or contact us for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. 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 highly recommended for safety and proper engine performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world reliability.
- Fast Global Fulfillment — We offer free standard delivery to most regions with a typical transit time of 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.
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