160°F Thermostat Kit for Volvo Penta and OMC 4.3L, 5.0L, 5.7L and 5.8L V6/V8 Engines – Replaces 3856961 and 18-3677
160°F Thermostat Kit for Volvo Penta and OMC 4.3L, 5.0L, 5.7L and 5.8L V6/V8 Engines – Replaces 3856961 and 18-3677 is backordered and will ship as soon as it is back in stock.
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160°F Thermostat Kit for Volvo Penta and OMC 4.3L, 5.0L, 5.7L and 5...
160°F Thermostat Kit for Volvo Penta and OMC 4.3L, 5.0L, 5.7L and 5.8L V6/V8 Engines – Replaces 3856961 and 18-3677 is backordered and will ship as soon as it is back in stock.
Product Details
This 160°F marine thermostat kit is designed for selected Volvo Penta and OMC sterndrive/inboard gasoline engines, including 4.3L V6, 5.0L V8, 5.7L V8 and 5.8L V8 applications. It is intended to help maintain the engine's specified operating temperature and is supplied as a service kit with the thermostat, gasket and O-ring.
The kit replaces the Volvo Penta thermostat reference 3856961 and the aftermarket reference 18-3677. Catalog references also associate thermostat 3856961 with OMC reference 383307. Always compare the original thermostat, engine model and cooling-system configuration before ordering.
- 160°F thermostat rating.
- Service kit for selected Volvo Penta and OMC applications.
- Includes the thermostat, gasket and O-ring required for the listed service.
- Aftermarket replacement component; not an OEM-branded part.
Part Number References
These are manufacturer or aftermarket catalog references associated with this thermostat application. They are provided for cross-reference purposes only and do not replace model and application verification.
| Brand or Reference Type | Part Number | Description |
|---|---|---|
| Volvo Penta | 3856961 | Thermostat reference |
| OMC / Volvo Penta catalog reference | 383307 | Thermostat reference |
| Aftermarket catalog reference | 18-3677 | 160°F thermostat kit |
Engine and Model Compatibility
The catalog application information associates the 3856961 thermostat with the following Volvo Penta engine families and model variants. Fitment can vary by year, cooling-system design, engine configuration and serial number, so confirm the original part number before installation.
| Brand | Engine Model or Variant | Displacement | Thermostat Rating | Reference |
|---|---|---|---|---|
| Volvo Penta | 4.3 GL, 4.3 GS, 4.3 Gi, 4.3 GXi-B, 4.3 GXi-BF | 4.3L V6 | 160°F / approximately 70°C | 3856961 |
| Volvo Penta | 5.0 FL, 5.0 Fi, 5.0 Gi, 5.0 GL | 5.0L V8 | 160°F / approximately 70°C | 3856961 |
| Volvo Penta | 5.7 GL, 5.7 Gi, 5.7 GS, 5.7 GSi, 5.7 GSX | 5.7L V8 | 160°F / approximately 70°C | 3856961 |
| Volvo Penta | 5.8 FL, 5.8 Fi, 5.8 FSi | 5.8L V8 | 160°F / approximately 70°C | 3856961 |
OMC catalog information also associates this 160°F thermostat application with selected 4.3L, 4.3HO, 5.0L and 5.8L engines. Confirm the exact OMC model, production year and serial-number range before purchase.
Technical Specifications
- Product Type
- Marine engine thermostat kit
- Thermostat Rating
- 160°F / approximately 71°C
- Application
- Selected Volvo Penta and OMC V6/V8 gasoline engines
- Installation
- Direct replacement when the original part number and application match
- Brand Status
- Aftermarket replacement, not OEM-branded
What's in the Box
- 1 x 160°F thermostat, associated with reference 3856961
- 1 x thermostat gasket
- 1 x O-ring
The gasket and O-ring are service components supplied with the kit. Individual catalog listings may identify these components under different component numbers; the kit contents above describe what is included with this product.
Installation Notes
- Allow the engine to cool completely before beginning service.
- Disconnect the battery and close any applicable water supply or seacock according to the engine manufacturer's service procedure.
- Drain the cooling system as required and place a suitable container beneath the thermostat housing.
- Remove the thermostat housing cover and note the orientation of the original thermostat.
- Remove the old thermostat, gasket and O-ring. Clean the mating surfaces carefully without damaging the housing.
- Install the new thermostat in the same orientation as the original component.
- Fit the supplied gasket and O-ring, then reinstall the housing cover.
- Tighten the housing fasteners to the engine manufacturer's specified torque. Do not overtighten.
- Refill or prime the cooling system using the procedure and fluid specified for the engine.
- Run the engine at idle, allow it to reach operating temperature and check the housing for leaks. Stop immediately if the engine overheats or coolant flow is abnormal.
Troubleshooting and FAQ
How do I confirm that this kit fits my engine?
Check the engine brand, exact model designation, displacement, cooling-system configuration and serial number. Then compare the original thermostat or catalog reference with 3856961, 383307 or 18-3677. Model names alone may not establish fitment across every production year.
What are common signs of a failing thermostat?
Possible symptoms include overheating, slow warm-up, an engine that runs cooler than specified, fluctuating temperature-gauge readings or inconsistent operating temperature. Cooling-system restrictions, impeller problems and sensor faults can produce similar symptoms and should also be checked.
Why is this thermostat rated at 160°F?
The 160°F rating is specified for the listed thermostat application. Use the temperature rating required by your engine manufacturer; do not substitute a different rating solely because the part appears physically similar.
Is this an OEM part?
No. This is an aftermarket replacement kit intended for applications associated with the listed manufacturer and catalog references. Volvo Penta and OMC are referenced only for product identification and fitment comparison.
Should I replace the gasket and O-ring during thermostat service?
Yes. The kit includes a replacement gasket and O-ring so the sealing components can be renewed during thermostat installation. Inspect the housing and cover for corrosion, pitting or damage before reassembly.
Safety and Important Information
- Never open a hot cooling system. Allow the engine to cool before removing the thermostat housing.
- Verify the original part number and the complete engine application before purchase.
- Do not use this listing to confirm fitment for an engine with a different thermostat rating or cooling-system configuration.
- Follow the engine manufacturer's service procedure and torque specifications.
- Professional installation is recommended when the correct cooling-system procedure or engine configuration is uncertain.
About Sea Sierra
- Marine Parts Focus — We supply replacement components for recreational marine engines and systems.
- Application-Conscious Listings — Product references and compatibility information are provided to help you compare the part with your original equipment.
- Service-Ready Components — Kits are packaged to support common maintenance and repair procedures when the application is confirmed.
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