Thermostat Kit – Fits Mercury/Mariner 40-60 HP 3-Cylinder Outboards (Replaces 850055A2)
Thermostat Kit – Fits Mercury/Mariner 40-60 HP 3-Cylinder Outboards (Replaces 850055A2) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat Kit – Fits Mercury/Mariner 40-60 HP 3-Cylinder Outboards...
Product Details
This Thermostat Kit – Fits Mercury/Mariner 40-60 HP 3-Cylinder Outboards (Replaces 850055A2) is designed for Mercury and Mariner 40-60 HP 3-cylinder, 2-stroke outboard engines manufactured from 1997 and later. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.
This kit serves as a direct replacement for Mercury part numbers 850055A2 and 850055A1, as well as GLM part number 13141, providing a reliable interchange solution.
- Engineered as a direct-fit replacement for straightforward installation.
- Maintains a consistent engine operating temperature of 110°F (43.3°C).
- Includes the thermostat and all necessary gaskets for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 850055A2 |
| Mercury | 850055A1 |
| GLM | 13141 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This part is designed for specific Mercury and Mariner outboard models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | 40 JET | 40 | 2-Stroke | 1997–Up | 850055A2 | 3 Cylinder |
| Mercury/Mariner | 45 JET | 45 | 2-Stroke | 1997–Up | 850055A2 | 3 Cylinder |
| Mercury/Mariner | 55 | 55 | 2-Stroke | 1997–Up | 850055A2 | 3 Cylinder |
| Mercury/Mariner | 60 | 60 | 2-Stroke | 1997–Up | 850055A2 | 3 Cylinder |
| Mercury/Mariner | 60 BIGFOOT | 60 | 2-Stroke | 1997–Up | 850055A2 | 3 Cylinder |
Technical Specs
- Product Type
- Thermostat Kit
- Installation
- Direct replacement
- Operating Temperature
- 110°F (43.3°C)
- Dimensions
- Length: 18.0 in, Width: 12.0 in, Height: 4.0 in
- Weight
- 0.17 kg (0.38 lb)
- Other Attributes
- Includes thermostat and necessary gaskets for installation
What’s in the Box
- 1 x Thermostat (850055/850055001)
- 1 x Gasket (827365/889735)
- 1 x Housing/Cover Gasket (854639/854639001/26-854639/26-854639001)
- 1 x Thermostat Cover (27-827284/827284/827251A1)
Installation Notes
- Disconnect the negative battery cable before starting.
- Allow the engine to cool completely. Partially drain the engine block coolant.
- Locate the thermostat housing on the engine block.
- Remove the bolts securing the thermostat housing cover.
- Carefully remove the old thermostat and gasket. Note the orientation of the thermostat.
- Thoroughly clean the mating surfaces of the housing and cover, removing any old gasket material.
- Install the new thermostat and gasket in the correct orientation.
- Reinstall the housing cover and tighten the bolts to the manufacturer-specified torque.
- Refill the cooling system with the appropriate coolant.
- Reconnect the battery, start the engine, and check for leaks and proper operating temperature.
Troubleshooting & FAQ
How do I confirm this kit fits my engine?
Verify your engine's model, horsepower, and year fall within the ranges listed in the "Engine & Model Compatibility" table. Cross-reference your existing part number with those in the "Part Number Matrix" for confirmation.
What are the signs of a failing thermostat?
Common symptoms include engine overheating at high speeds, running too cold at idle (or trolling speeds), inconsistent temperature gauge readings, and increased fuel consumption. A thermostat stuck open will prevent the engine from reaching operating temperature, while one stuck closed will cause overheating.
Can I replace this thermostat myself?
Yes, this is a common DIY task for those with basic mechanical skills. However, it requires care to ensure surfaces are clean and bolts are torqued correctly to prevent leaks. Always consult your engine’s service manual for detailed procedures. When in doubt, professional installation is recommended.
Is this 110°F temperature correct for my outboard?
Yes, many 2-stroke outboards, especially those operated in saltwater, use a lower-temperature thermostat (around 110°F–120°F) to prevent salt and mineral deposits from building up inside the cooling passages, which can occur at higher temperatures.
How often should an outboard thermostat be replaced?
It's good practice to inspect the thermostat annually and consider replacement every 2-3 years or 200-300 hours, especially if operating in saltwater. This is a preventative measure to avoid an unexpected failure that could lead to engine damage.
What happens if I use the wrong gasket?
Using incorrect or damaged gaskets will cause coolant leaks, leading to inefficient cooling and potential overheating. This kit includes the specific gaskets required for a proper seal on the listed compatible engines.
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
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