Thermostat Kit (120°) – Fits Mercury Marine 6-25 HP 2-Stroke Outboards (Replaces 14586A3)
Thermostat Kit (120°) – Fits Mercury Marine 6-25 HP 2-Stroke Outboards (Replaces 14586A3) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Thermostat Kit (120°) – Fits Mercury Marine 6-25 HP 2-Stroke Outboa...
Product Details
This Thermostat Kit (120°) – Fits Mercury Marine 6-25 HP 2-Stroke Outboards (Replaces 14586A3) contains a 120°F (50°C) thermostat and all necessary gaskets for Mercury Marine 2-stroke outboards. It is designed for Mercury/Mariner outboards from 6 HP to 25 HP manufactured between 1984 and 1998, ensuring your engine maintains the correct operating temperature for optimal performance and longevity.
This kit is a direct replacement for Mercury part numbers 14586A3 and 75692A11, and also interchanges with parts from Sierra, GLM, and Mallory.
- Ensures engine operates at the correct 120°F (50°C) temperature.
- Designed for a direct-fit installation, no modifications needed.
- Includes a complete set of gaskets and an O-ring for a comprehensive service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 14586A3 |
| Mercury | 75692A11 |
| Mercury | 75692A10 |
| Mercury | 75692A9 |
| Sierra | 18-3549 |
| Sierra | 18-43052 |
| Sierra | 18-0323 |
| GLM | 13121 |
| Mallory | 9-43052 |
| Mallory | 9-43014 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit fits a range of Mercury and Mariner outboards. Verify your model and serial number against the details provided to ensure accurate fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | Standard | 6 | 2-Stroke | 1986–1998 | 14586A3 | Serial Range: 0A197112 & Up (USA) |
| Mercury | Standard | 6 | 2-Stroke | 1986–1993 | 14586A3 | Serial Range: 9461526 & Up (BEL) |
| Mercury | Standard | 8 | 2-Stroke | 1986–1998 | 14586A3 | Serial Range: 0A197112 & Up (USA) |
| Mercury | Standard | 8 | 2-Stroke | 1986–1993 | 14586A3 | Serial Range: 9461526 & Up (BEL) |
| Mercury | Standard | 9.9 | 2-Stroke | 1986–1998 | 14586A3 | Serial Range: 0A197112 & Up (USA) |
| Mercury | Standard | 9.9 | 2-Stroke | 1986–1993 | 14586A3 | Serial Range: 9461526 & Up (BEL) |
| Mercury | Standard | 15 | 2-Stroke | 1988–1998 | 14586A3 | Serial Range: 0B292414 & Up (USA) |
| Mercury | Standard | 15 | 2-Stroke | 1988–1993 | 14586A3 | Serial Range: 9542620 & Up (BEL) |
| Mercury | Sea Pro | 15 | 2-Stroke | 1994–1998 | 14586A3 | Serial Range: 0G044365 & Up (USA) |
| Mercury | Sea Pro | 15 | 2-Stroke | 1997–1998 | 14586A3 | Serial Range: 9927000 & Up (BEL) |
| Mercury | Super | 15 | 2-Stroke | 1988–1998 | 14586A3 | Serial Range: 0B238464 & Up (USA) |
| Mercury | Super | 15 | 2-Stroke | 1988–1998 | 14586A3 | Serial Range: 9507381 & Up (BEL) |
| Mercury | Super | 15 | 2-Stroke | 1988–1998 | 14586A3 | Serial Range: 0A730007 & Up (CAN) |
| Mercury | Standard | 20 | 2-Stroke | 1986–1987 | 14586A3 | Serial Range: 0B114231 & Up (USA) |
| Mercury | Standard | 20 | 2-Stroke | 1986–1987 | 14586A3 | Serial Range: 9467988 & Up (BEL) |
| Mercury | Standard | 20 | 2-Stroke | 1986–1987 | 14586A3 | Serial Range: 0A719661 & Up (CAN) |
| Mercury | Standard | 25 | 2-Stroke | 1984–1987 | 14586A3 | Serial Range: 0B114231 & Up (USA), 2-Cylinder |
| Mercury | Standard | 25 | 2-Stroke | 1984–1987 | 14586A3 | Serial Range: 9467988 & Up (BEL), 2-Cylinder |
| Mercury | Standard | 25 | 2-Stroke | 1984–1987 | 14586A3 | Serial Range: 0A719661 & Up (CAN), 2-Cylinder |
| Mercury | Sea Pro | 25 | 2-Stroke | 1988–1998 | 14586A3 | Serial Range: 0B238464 & Up (USA) |
| Mercury | Sea Pro | 25 | 2-Stroke | 1988–1994 | 14586A3 | Serial Range: 9507381 & Up (BEL) |
| Mercury | Sea Pro | 25 | 2-Stroke | 1988–1994 | 14586A3 | Serial Range: 0A730007 & Up (CAN) |
Technical Specs
- Product Type
- Thermostat Kit
- Installation
- Direct Replacement
- Operating Temperature
- 120°F (50°C) nominal
- Package Contents
- Thermostat (120°F), Multiple Gaskets, O-ring
- Compatibility
- Mercury/Mariner 6-25 HP 2-Stroke (1984–1998)
- OEM Part Number
- 14586A3
- Package Dimensions
- 7.0" L x 6.0" W x 0.75" H
What’s in the Box
- 1 x Thermostat (120°F) (14586)
- 1 x Gasket (19205)
- 1 x Gasket (62386)
- 1 x Gasket (14318)
- 1 x O-ring
Installation Notes
- Ensure the engine is completely cool before starting. Disconnect the battery for safety.
- Locate the thermostat housing on the engine block. Place a drain pan underneath to catch any residual coolant.
- Carefully remove the bolts securing the housing cover. Note their orientation if they are different lengths.
- Gently pry the cover off. If it is stuck, tap it lightly with a rubber mallet; do not use a screwdriver, as it can damage the sealing surfaces.
- Remove the old thermostat and gaskets. Clean both sealing surfaces on the engine and the cover thoroughly, removing all old gasket material.
- Compare the new thermostat and gaskets to the old ones to ensure a perfect match.
- Install the new thermostat in the correct orientation. Place the correct new gasket for your model onto the housing.
- Reinstall the housing cover and tighten the bolts evenly in a crisscross pattern to the manufacturer's specified torque.
- Reconnect the battery, start the engine, and check for leaks as it warms up to operating temperature.
Troubleshooting & FAQ
How do I know if this thermostat fits my engine?
The best way is to check your serial number. Compare it to the ranges listed in the "Engine & Model Compatibility" table. If your engine's model, year, and serial number align with a row in the table, the kit will fit.
What are the signs of a bad thermostat?
Common symptoms include engine overheating (stuck closed) or taking too long to reach operating temperature (stuck open). You might also notice poor engine performance, increased fuel consumption, or steam from the exhaust.
This kit includes multiple gaskets. Which ones do I use?
This kit is designed to cover multiple engine variations. Compare the old gaskets from your specific engine model to the new ones provided in the kit. Use the new gaskets that are an exact match to your old ones.
How often should a thermostat be replaced?
Thermostats don't have a strict replacement interval, but it is good practice to inspect them during regular cooling system service or replace them every 3-5 years, especially if operating in saltwater. They should be replaced immediately if you notice any signs of failure.
Is 120°F the correct temperature for my engine?
Yes, this 120°F (50°C) thermostat is the specified temperature for the listed Mercury and Mariner outboard models. Using the correct temperature thermostat is critical for engine performance, preventing carbon buildup, and ensuring fuel efficiency.
Why does my OEM part number not match 14586A3 exactly?
Your part may be a superseded number. Manufacturers often update part numbers over time. This kit replaces the entire supersession chain, including 75692A11, 75692A10, and 75692A9, all of which are succeeded by 14586A3.
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.
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