Thermostat – Fits Mercury/Mariner F40/F50/F60 EFI 4-Cylinder 4-Stroke Outboards (Replaces 8M0117413, 8M0168892)
Thermostat – Fits Mercury/Mariner F40/F50/F60 EFI 4-Cylinder 4-Stroke Outboards (Replaces 8M0117413, 8M0168892) is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
Thermostat – Fits Mercury/Mariner F40/F50/F60 EFI 4-Cylinder 4-Stro...
Thermostat – Fits Mercury/Mariner F40/F50/F60 EFI 4-Cylinder 4-Stroke Outboards (Replaces 8M0117413, 8M0168892) is backordered and will ship as soon as it is back in stock.
Product Details
This is a replacement Thermostat – Fits Mercury/Mariner F40/F50/F60 EFI 4-Cylinder 4-Stroke Outboards (Replaces 8M0117413, 8M0168892). It is designed for 40, 50, and 60 HP 4-cylinder EFI models with serial numbers 1C050252 and higher, regulating engine temperature for optimal performance and longevity.
This part is a direct interchange for Mercury OEM parts 8M0117413 and 8M0168892, as well as Sierra 18-3640 and OMAX 8M0117413.
- Engineered for direct-fit installation in the original thermostat housing.
- Built with corrosion-resistant materials for saltwater and freshwater environments.
- Includes one thermostat, ready for installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury / Mariner | 8M0117413 |
| Mercury / Mariner | 8M0168892 |
| Sierra | 18-3640 |
| OMAX | 8M0117413 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury/Mariner Owners: This thermostat fits specific 4-cylinder EFI 4-stroke outboards (40, 50, 60 HP) within the serial number range 1C050252 and up. Please verify your engine's serial number before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | F40 EFI | 40 | 4-Stroke | Serial: 1C050252 & up | 8M0117413/8M0168892 | 4-cylinder |
| Mercury | F50 EFI | 50 | 4-Stroke | Serial: 1C050252 & up | 8M0117413/8M0168892 | 4-cylinder |
| Mercury | F60 EFI | 60 | 4-Stroke | Serial: 1C050252 & up | 8M0117413/8M0168892 | 4-cylinder |
Technical Specs
- Product Type
- Marine Engine Thermostat
- Installation
- Direct replacement in thermostat housing
- Temperature Rating
- 122°F / 50°C
- Material
- Durable corrosion-resistant construction
- Operating Environment
- Marine (salt/fresh water)
- Engine Type
- 4-Stroke EFI outboard
- Application
- Engine cooling system regulation
What’s in the Box
- 1 x 122°F/50°C Outboard Thermostat (Replaces 8M0117413/8M0168892)
Installation Notes
- Disconnect the battery to prevent accidental starting.
- Allow the engine to cool completely before beginning work.
- Locate the thermostat housing on the engine block. Place a drain pan underneath.
- Carefully remove the bolts securing the housing cover. Note any coolant that drains out.
- Remove the old thermostat and any gasket or sealing material.
- Clean both the housing and cover mating surfaces thoroughly.
- Install the new thermostat in the correct orientation.
- Re-install the housing cover with a new gasket (if required) and tighten bolts to manufacturer specifications.
- Refill the engine cooling system with the recommended coolant.
- Reconnect the battery, start the engine, and check for leaks and proper temperature gauge operation.
Troubleshooting & FAQ
How can I confirm this thermostat fits my engine?
This part fits Mercury/Mariner 40, 50, and 60 HP 4-cylinder EFI outboards with a serial number of 1C050252 or higher. The most reliable way to confirm fitment is to check your engine's serial number against this range. You can also cross-reference your existing part number with the numbers listed in our Part Number Matrix.
What are the signs of a faulty thermostat?
Common symptoms include engine overheating (stuck closed) or taking too long to warm up to operating temperature (stuck open). You may see a temperature alarm on your gauges, notice steam from the engine, or experience poor performance and efficiency.
What is the operating temperature of this thermostat?
This thermostat is rated to open at 122°F / 50°C, helping your engine maintain its ideal operating temperature for performance and fuel efficiency.
Can I install this myself?
While installation is straightforward for those with mechanical experience, we recommend professional installation to ensure it's done correctly. Improper installation can lead to coolant leaks and engine overheating.
Does this include a new gasket?
This listing includes the thermostat only. The thermostat housing gasket is sold separately and should be replaced during installation to ensure a proper seal.
How often should an outboard thermostat be replaced?
Thermostats don't have a fixed replacement interval, but it's good practice to inspect them during regular cooling system service (e.g., every 300 hours or 3 years) and replace them if there are signs of corrosion or if the engine shows symptoms of poor temperature regulation.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
