143°F / 62°C Thermostat for Johnson/Evinrude 2-Stroke Outboards – Replaces 0394411, 0778199
143°F / 62°C Thermostat for Johnson/Evinrude 2-Stroke Outboards – Replaces 0394411, 0778199 is backordered and will ship as soon as it is back in stock.
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143°F / 62°C Thermostat for Johnson/Evinrude 2-Stroke Outboards – R...
143°F / 62°C Thermostat for Johnson/Evinrude 2-Stroke Outboards – Replaces 0394411, 0778199 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket 143°F / 62°C Vernatherm thermostat is designed for selected Johnson and Evinrude two-stroke outboards. It helps regulate engine operating temperature by opening at approximately 62°C (143°F) when the specified temperature is reached.
The thermostat replaces the listed Johnson/Evinrude/OMC references 394411, 0394411, 778199, and 0778199. The company listing also identifies Sierra Marine 18-1506 as an equivalent aftermarket reference.
- Aftermarket replacement thermostat for selected Johnson/Evinrude outboards.
- 143°F / 62°C opening temperature.
- Sold as a single thermostat component, not as a multi-piece kit.
- Confirm the complete engine model, year, stroke, and original thermostat reference before ordering.
Part Number Matrix
Use these references to compare the thermostat with the part installed on your engine. Part-number similarity alone does not confirm fitment.
| Brand or Reference | Part Number |
|---|---|
| Johnson/Evinrude/OMC | 394411 / 0394411 |
| Johnson/Evinrude/OMC | 778199 / 0778199 |
| Sierra Marine | 18-1506 |
| GLM | 13190 |
Engine & Model Compatibility
The following horsepower, stroke, and year combinations are listed for this thermostat. Verify the exact engine model and serial-number range in your service information before installation.
| Brand | Rated HP | Stroke | Years | Listed OEM Reference | Application Notes |
|---|---|---|---|---|---|
| Johnson/Evinrude | 10 / 15 | 2-Stroke | 1993–1995 | 0394411 / 394411 | Big Bore applications |
| Johnson/Evinrude | 60 / 125 / 185 | 2-Stroke | 1989–1990 | 0394411 / 394411 | Use only where the original thermostat reference matches |
| Johnson/Evinrude | 65 | 2-Stroke | 1987–1989 | 0394411 / 394411 | Verify the exact model before ordering |
| Johnson/Evinrude | 70 / 200 / 225 | 2-Stroke | 1986–1990 | 0394411 / 394411 | Verify the exact model before ordering |
| Johnson/Evinrude | 120 / 140 / 300 | 2-Stroke | 1985–1990 | 0394411 / 394411 | Verify the exact model before ordering |
| Johnson/Evinrude | 275 | 2-Stroke | 1985–1988 | 0394411 / 394411 | Verify the exact model before ordering |
The company reference also mentions Vernatherm applications for 65, 85, 100, 115, and 135 HP engines. Because complete year and model conditions are not provided for those additional references, confirm the original part number and service-manual application before purchase.
Technical Specifications
- Product Type
- Aftermarket outboard engine thermostat
- Thermostat Style
- Vernatherm-style thermostat
- Temperature Rating
- 143°F / 62°C
- Opening Temperature
- Approximately 62°C (143°F)
- Engine Type
- Selected Johnson/Evinrude two-stroke outboards
- Replacement References
- 394411, 0394411, 778199, 0778199
- Aftermarket Reference
- Sierra Marine 18-1506
- Product Configuration
- Single thermostat component
What’s in the Box
- 1 x 143°F / 62°C aftermarket thermostat
This listing is for the thermostat component. Confirm whether your engine requires a separate gasket, seal, or other installation hardware before beginning the repair.
Installation Notes
- Switch off the engine, allow it to cool completely, and follow the safety procedures in the service manual.
- Disconnect the battery if required by the manufacturer’s service procedure.
- Locate the thermostat housing and note the orientation of the existing thermostat before removal.
- Remove the housing cover carefully and take out the old thermostat and sealing components.
- Clean the mating surfaces without damaging the housing or cylinder-head sealing area.
- Install the replacement thermostat in the same orientation as the original part.
- Install the correct new gasket or seal if required for your specific engine. Do not reuse damaged sealing components.
- Reinstall the thermostat cover and tighten the fasteners to the manufacturer’s specified torque.
- Restore the cooling-system configuration, start the engine according to the service manual, and check for leaks and normal water flow.
- Stop the engine immediately if it overheats, leaks, or shows abnormal temperature behavior.
Troubleshooting & FAQ
What does this thermostat do?
It controls coolant or cooling-water flow through the outboard’s cooling system to help the engine reach and maintain its specified operating temperature. This model is listed with a 143°F / 62°C opening temperature.
Which engines does it fit?
It is listed for selected Johnson/Evinrude two-stroke applications, including the horsepower and year combinations shown in the compatibility table. Always verify the complete model and original part number because engines with the same horsepower rating may use different components.
Is this thermostat for four-stroke engines?
No four-stroke applications are identified for this listing. It is intended for the specified Johnson/Evinrude two-stroke applications only.
Does the listing include a gasket?
The company record identifies this product as a single thermostat component and does not specify a gasket in the package contents. Check your engine’s parts diagram and obtain the correct gasket or seal separately if required.
How can I tell if my thermostat needs replacement?
Possible symptoms include overheating, running below the normal operating temperature, slow warm-up, or inconsistent temperature behavior. Inspect the thermostat and cooling passages according to the engine service manual before replacing parts.
Can I install it myself?
Thermostat replacement may be suitable for an experienced owner with the correct tools and service information. If you are uncertain about the thermostat orientation, sealing procedure, or torque specifications, use a qualified marine technician.
Is this an OEM thermostat?
No. This is an aftermarket replacement listed to replace the referenced Johnson/Evinrude/OMC part numbers and cross-reference numbers.
Safety & Important Information
- Verify the exact engine model, year, stroke, serial-number range, and original thermostat reference before ordering.
- Do not rely on horsepower alone to confirm compatibility.
- Never work on a hot engine or open the thermostat housing before the engine has cooled.
- Use the manufacturer’s service manual for installation orientation, gasket requirements, torque values, and cooling-system checks.
- This is an aftermarket replacement component, not an original manufacturer part.
About Sea Sierra
- Marine Replacement Parts — We provide aftermarket components for common marine repair and maintenance applications.
- Application-Focused Listings — Product references and fitment details are provided to help you compare the replacement part with your original component.
- Verify Before Installation — Always compare the part number, physical design, and engine application with your service information before fitting a replacement part.
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