160°F Thermostat Kit for OMC Cobra Sterndrives – Replaces 383307 and Sierra 18-3653
160°F Thermostat Kit for OMC Cobra Sterndrives – Replaces 383307 and Sierra 18-3653 is backordered and will ship as soon as it is back in stock.
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160°F Thermostat Kit for OMC Cobra Sterndrives – Replaces 383307 an...
160°F Thermostat Kit for OMC Cobra Sterndrives – Replaces 383307 and Sierra 18-3653 is backordered and will ship as soon as it is back in stock.
Product Details
This 160°F (71°C) thermostat kit is designed for OMC Cobra and OMC sterndrive cooling systems. It replaces the OMC thermostat kit associated with OEM number 383307 and Sierra kit number 18-3653.
This listing specifies use on OMC engines from 1993 and earlier, except 4-cylinder GM applications from 1980 and later. The catalog application range includes OMC Cobra engines in 2.3L, 2.5L, 3.0L, 4.3L, 4.6L, 5.0L, 5.7L, 5.8L, and 7.5L configurations within the applicable model years listed below.
- 160°F (71°C) thermostat rating.
- Complete service kit with thermostat and application-specific gaskets.
- Direct aftermarket replacement for the listed OMC and Sierra references.
- Verify the engine model, year, cooling-system configuration, and original part before ordering.
Part Number Matrix
These references identify the thermostat kit or its documented component references. Part-number matching alone does not replace confirmation of the complete engine application.
| Brand or Reference | Part Number | Reference Type |
|---|---|---|
| OMC | 383307 | OEM thermostat reference |
| OMC | 379754 | OEM reference listed for the kit |
| OMC | 3852216 | OEM reference listed for the kit |
| OMC | 778056 | OEM reference listed for the kit |
| Sierra | 18-3653 | Thermostat kit reference |
| Sierra | 18-3653D | Display-packaged kit reference |
| Sierra | 18-3677 | Related 160°F thermostat kit reference |
| Sierra | 18-3554 | 160°F thermostat component reference |
| Volvo Penta | 3856961 | Thermostat reference associated with the catalog mapping; confirm application separately |
| GLM | 13430, 13060 | Aftermarket references |
| Mallory | 9-43156, 9-43021 | Aftermarket references |
Engine & Model Compatibility
The primary this listing is OMC engines from 1993 and earlier, excluding 4-cylinder GM applications from 1980 and later. The following displacement and year ranges are catalog application references and should be checked against the exact engine model before installation.
| Brand / Drive | Engine Displacement | Applicable Years | Notes |
|---|---|---|---|
| OMC Cobra | 2.3L | 1987–1990 | Confirm exact engine configuration. |
| OMC Cobra | 2.5L | 1986 | Confirm exact engine configuration. |
| OMC Cobra | 3.0L | 1986–1993 | Not for the excluded 4-cylinder GM applications from 1980 and later. |
| OMC Cobra | 4.3L | 1986–1993 | Confirm exact engine configuration. |
| OMC Cobra | 4.6L | 1989 | Confirm exact engine configuration. |
| OMC Cobra | 5.0L | 1986–1993 | Confirm exact engine configuration. |
| OMC Cobra | 5.7L | 1986–1993 | Confirm exact engine configuration. |
| OMC Cobra | 5.8L | 1989–1993 | Confirm exact engine configuration. |
| OMC Cobra | 7.5L | 1987–1989 | Confirm exact engine configuration. |
Technical Specs
- Product Type
- Marine engine thermostat kit
- Temperature Rating
- 160°F (71°C)
- Application
- OMC sterndrive and Cobra cooling systems
- Engine Range
- OMC 2.3L, 2.5L, 3.0L, 4.3L, 4.6L, 5.0L, 5.7L, 5.8L, and 7.5L applications listed above
- Fitment Limitation
- Except 4-cylinder GM applications from 1980 and later, unless specifically confirmed for the exact engine
- Replacement Type
- Aftermarket replacement thermostat kit
What’s in the Box
- 1 x 160°F thermostat
- 1 x manifold gasket
- 1 x GM thermostat gasket
- 1 x thermostat gasket
The kit contents follow this listing. The catalog identifies the gasket references as 314809, 3701777 (GM), and 3852111.
Installation Notes
- Disconnect the battery and allow the engine to cool completely before servicing the cooling system.
- Drain coolant as needed to lower the level below the thermostat housing.
- Remove the thermostat housing and note the original thermostat orientation.
- Remove the old thermostat and gasket material, then clean the mating surfaces thoroughly.
- Install the new thermostat in the correct orientation with the applicable gasket for your engine configuration.
- Reinstall the housing and tighten the fasteners to the engine manufacturer’s specified torque.
- Reconnect hoses, refill the cooling system with the correct coolant mixture, and bleed air as required.
- Start the engine and check carefully for leaks while monitoring the temperature gauge.
Troubleshooting & FAQ
What are the signs of a failing thermostat?
Common signs include overheating, unusually slow warm-up, temperature fluctuations, or an engine that does not reach its normal operating temperature. Inspect the cooling system for other causes before replacing the thermostat.
Is this a 160°F thermostat?
Yes. The thermostat kit is rated at 160°F (71°C). Confirm that this temperature rating and the kit contents match the requirements for your exact OMC engine.
Does this fit every OMC engine?
No. This listing is for OMC engines from 1993 and earlier, with the stated exclusion for 4-cylinder GM applications from 1980 and later. Verify the engine displacement, year, model, and original thermostat reference before ordering.
Is this an OEM part?
No. This is an aftermarket replacement kit intended to replace the listed OEM and aftermarket references.
How often should a marine thermostat be inspected?
Inspect the thermostat during routine cooling-system service and whenever the engine shows abnormal temperature behavior. Saltwater use and corrosion can shorten service life.
Safety & Important Information
- Confirm fitment using the exact engine model, year, displacement, cooling-system configuration, and original part number.
- Do not rely on displacement alone when selecting a thermostat kit.
- Use the applicable gasket supplied for the engine configuration; do not install unused gaskets where they are not required.
- Allow the engine to cool before opening the cooling system.
- Professional installation is recommended if you are not familiar with marine engine cooling systems.
About Sea Sierra
- Marine Parts Focus — Replacement components for marine cooling and sterndrive service.
- Application-Focused Listings — Product references and fitment details are provided to support accurate part selection.
- Service-Ready Kits — This kit combines the thermostat and documented application gaskets for a complete thermostat service.
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