140°F Thermostat & Gasket Kit for Mercury 4-Stroke Outboards – 8–30 HP
140°F Thermostat & Gasket Kit for Mercury 4-Stroke Outboards – 8–30 HP is backordered and will ship as soon as it is back in stock.
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140°F Thermostat & Gasket Kit for Mercury 4-Stroke Outboards – ...
140°F Thermostat & Gasket Kit for Mercury 4-Stroke Outboards – 8–30 HP is backordered and will ship as soon as it is back in stock.
Product Details
This 140°F (60°C) thermostat and gasket kit is designed for selected Mercury Marine 4-stroke outboards from 8 through 30 HP. It helps regulate engine operating temperature and supports proper cooling-system performance.
The thermostat is listed for Mercury applications under OEM reference 8M0119207. Application listings identify the part in cylinder-block applications for specific 8, 9.9, 10, 15, 20, 25, and 30 HP 4-stroke engines. Always verify the complete model and serial-number condition before ordering.
- Aftermarket replacement thermostat and gasket kit.
- 140°F (60°C) temperature rating.
- Intended for the listed Mercury 4-stroke outboard cooling-system applications.
- Kit includes the thermostat, housing gasket, and rubber seal as described below.
Part Number References
Use the following reference to compare the replacement with your original part. Reference numbers are application identifiers and should not be treated as confirmation of fitment without checking the engine model and serial number.
| Brand | Part Number |
|---|---|
| Mercury | 8M0119207 |
| Mercury | 855676003 |
Engine & Model Compatibility
The applications below are for OEM reference 8M0119207. The model, stroke, horsepower, and serial-number condition must be considered together; an engine that shares the same horsepower may still use a different component outside the stated serial range.
| Brand | Model | Rated HP | Stroke | Serial Condition | Catalog Location |
|---|---|---|---|---|---|
| Mercury | 8 (209cc) | 8 | 4-Stroke | 0P325500 & Up | Cylinder Block |
| Mercury | 8 (209cc) | 8 | 4-Stroke | 0R042475 & Up | Cylinder Block |
| Mercury | 9.9 (209cc) | 9.9 | 4-Stroke | 0P325500 & Up | Cylinder Block |
| Mercury | 9.9 (209cc) | 9.9 | 4-Stroke | 0R042475 & Up | Cylinder Block |
| Mercury | 10 Carb, 2-Cylinder | 10 | 4-Stroke | 0R575531 & Up | Cylinder Block |
| Mercury | 15 Carb, 2-Cylinder | 15 | 4-Stroke | 0R235949 & Up | Cylinder Block |
| Mercury | 15 Carb, 2-Cylinder JCI | 15 | 4-Stroke | 0R558208 & Up | Cylinder Block |
| Mercury | 15 SeaPro | 15 | 4-Stroke | 0R051685–0R123564 | Cylinder Block |
| Mercury | 15 SeaPro | 15 | 4-Stroke | 0R123565 & Up | Cylinder Block |
| Mercury | 20 Carb, 2-Cylinder | 20 | 4-Stroke | 0R235168 & Up | Cylinder Block |
| Mercury | 25 SeaPro | 25 | 4-Stroke | 0R051710 & Up | Cylinder Block |
| Mercury | 25 EFI, 3-Cylinder | 25 | 4-Stroke | 0R106999 & Up | Cylinder Block |
| Mercury | 25 Jet EFI, 3-Cylinder | 25 | 4-Stroke | 0R165086 & Up | Cylinder Block |
| Mercury | 30 EFI, 3-Cylinder | 30 | 4-Stroke | 0R106999 & Up | Cylinder Block |
Technical Specifications
- Product Type
- Aftermarket engine thermostat and gasket kit
- Temperature Rating
- 140°F (60°C)
- Application
- Marine outboard engine cooling system
- Installation
- Replacement installation in the thermostat housing
- Reference OEM Number
- 8M0119207
- Package Contents
- Thermostat, thermostat housing gasket, and rubber seal
What's in the Box
- 1 × 140°F thermostat
- 1 × thermostat rubber seal
- 1 × thermostat housing gasket
Installation Notes
- Make sure the engine is completely cool before beginning work. Follow the engine manufacturer's safety instructions and disconnect the battery where appropriate.
- Locate the thermostat housing on the cylinder block and place a suitable container beneath the area.
- Remove the housing fasteners and carefully separate the cover from the old gasket.
- Note the orientation of the old thermostat, then remove the thermostat, gasket, and rubber seal.
- Clean the mating surfaces thoroughly and remove old gasket material without damaging the housing or cylinder block.
- Install the new thermostat, gasket, and rubber seal in the correct orientation.
- Reinstall the housing cover and tighten the fasteners to the manufacturer's specified torque. Do not overtighten.
- Run the engine according to the manufacturer's procedure and check the housing area for leaks and proper cooling-system operation.
Troubleshooting & FAQ
How do I know if my thermostat may be failing?
Possible symptoms include overheating, an engine that runs colder than expected, failure to reach normal operating temperature, or unstable temperature behavior. Inspect the cooling system and follow the engine manufacturer's diagnostic procedure before replacing parts.
What temperature is this thermostat?
This replacement thermostat is rated at 140°F (60°C). Confirm that this rating and the complete serial-number application match your engine before installation.
Should I replace the gasket and seal with the thermostat?
Replacing the gasket and rubber seal during thermostat service helps provide a reliable seal after the housing is opened. This listing is supplied as a thermostat and gasket kit.
Does the part fit every Mercury outboard from 8 to 30 HP?
No. The horsepower range is only a general guide. Fitment depends on the exact model, 4-stroke configuration, and serial-number condition shown in the compatibility table. Verify your engine identification before ordering.
Is this an OEM Mercury part?
No. This is an aftermarket replacement that references Mercury OEM number 8M0119207. It is not represented as a genuine Mercury-manufactured component.
How often should an outboard thermostat be replaced?
There is no universal replacement interval for every engine. Inspect the thermostat during cooling-system service and replace it if it is sticking, corroded, damaged, contaminated, or associated with abnormal engine temperature.
What are your shipping speeds and costs?
Standard shipping is free to most regions. Typical transit time is 5–15 days, while available expedited options and costs are displayed at checkout.
Returns and product support
For return eligibility, deadlines and instructions, see SeaSierra’s Refund Policy. Contact SeaSierra before ordering if you need product-specific warranty information.
Safety & Important Information
- Verify the engine model, stroke, horsepower, and serial number together before purchase.
- Do not rely on horsepower alone to confirm fitment.
- Allow the engine to cool completely before opening the thermostat housing.
- This is an aftermarket replacement, not a genuine OEM component.
- Professional installation is recommended when the correct torque, orientation, or cooling-system service procedure is uncertain.
About Sea Sierra
- Marine Replacement Parts — We supply aftermarket components for common marine service and repair applications.
- Global Fulfillment — Standard delivery is available to most regions, with estimated transit times shown at checkout.
- Application-Focused Support — Compare the original part and verify complete engine identification before ordering.
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