Thermostat Kit – Fits Mercury/Mariner Verado V6/V8 175-300HP (Replaces 8M0162139, 8M0137816)
Thermostat Kit – Fits Mercury/Mariner Verado V6/V8 175-300HP (Replaces 8M0162139, 8M0137816) is backordered and will ship as soon as it is back in stock.
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Thermostat Kit – Fits Mercury/Mariner Verado V6/V8 175-300HP (Repla...
Thermostat Kit – Fits Mercury/Mariner Verado V6/V8 175-300HP (Replaces 8M0162139, 8M0137816) is backordered and will ship as soon as it is back in stock.
Product Details
This Thermostat Kit – Fits Mercury Verado V6/V8 175-300HP is essential for maintaining optimal engine temperature in Mercury and Mariner Verado 4-Stroke outboards (V6 3.4L & V8 4.6L, 175-300HP) manufactured from 2018 onwards (serial number 2B529482 and above).
It is a direct replacement for Mercury OEM part numbers 8M0162139 and its superseded predecessor, 8M0137816, ensuring a precise fit and reliable performance.
- Engineered as a direct-fit replacement for straightforward installation.
- Features a corrosion-resistant stainless steel housing for durability in marine environments.
- Incorporates a self-cleaning design to flush contaminants and maintain thermal efficiency.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By |
|---|---|---|
| Mercury | 8M0137816 | 8M0162139 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury and Mariner models, this part fits specific V6 and V8 Verado, Pro XS, SeaPro, and Racing engines from 2018 to the present. Always verify your engine's serial number against the ranges provided.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | Verado 3.4L V6 | 175 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 3.4L V6 Pro XS | 175 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 3.4L V6 | 200 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 3.4L V6 SeaPro | 200 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 Pro XS | 200 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | APEX | 200 | 4-Stroke | 2023–Present | 8M0162139 | S/N: 1E054353 and above |
| Mercury | Verado 3.4L V6 | 225 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 Pro XS | 225 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 SeaPro | 225 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 | 250 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 Pro XS | 250 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 SeaPro | 250 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 Verado | 250 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | 4.6L V8 Racing | 250R | 4-Stroke | 2021–Present | 8M0162139 | S/N: 1E080500 and above |
| Mercury | Verado 4.6L V8 | 300 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 Pro XS | 300 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 SeaPro | 300 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 Verado | 300 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | Verado 4.6L V8 Verado SeaPro | 300 | 4-Stroke | 2018–Present | 8M0162139 | S/N: 2B529482 and above |
| Mercury | 4.6L V8 Racing | 300R | 4-Stroke | 2021–Present | 8M0162139 | S/N: 1E080500 and above |
| Mercury | 4.6L V8 AMS Racing | 300R | 4-Stroke | 2021–Present | 8M0162139 | S/N: 1E081459 and above |
| Mercury | APEX | 360 | 4-Stroke | 2023–Present | 8M0162139 | S/N: 1E054247 and above |
| Mercury | Racing | 450R | 4-Stroke | 2020–2023 | 8M0162139 | S/N: 1E083006-1E099720 |
Technical Specs
- Product Type
- Thermostat
- Installation
- Direct replacement
- Housing Material
- Corrosion-resistant stainless steel
- Temperature Rating
- 140°F (60°C)
- Other Technical Attributes
- Self-cleaning design allows cooling system contaminants to flush through closing surfaces
What’s in the Box
- 1 x Thermostat (8M0162139)
Installation Notes
- Ensure the engine is completely cool and disconnect the battery for safety.
- Locate the thermostat housing on the engine. Place a drain pan underneath to catch any residual coolant.
- Carefully remove the housing bolts and cover. Note the orientation of the old thermostat before removing it.
- Clean the mating surfaces of the housing and cover, removing any old gasket material or sealant residue.
- Install the new thermostat, ensuring it is seated in the correct orientation.
- Reinstall the cover, using a new gasket if applicable, and tighten the bolts to the manufacturer's specified torque.
- Refill the cooling system with the recommended coolant and check for leaks.
- Reconnect the battery, start the engine, and allow it to reach operating temperature, verifying that the thermostat opens correctly.
Troubleshooting & FAQ
How do I know if my Verado's thermostat is failing?
Common signs of a faulty thermostat include engine overheating at low speeds, running too cool at cruising speeds (stuck open), or erratic temperature gauge readings. A stuck-closed thermostat will cause rapid overheating, while a stuck-open one will prevent the engine from reaching its ideal operating temperature, leading to poor fuel economy and increased engine wear.
What happens if I use a thermostat with the wrong temperature rating?
Using a thermostat with a rating different from the OEM 140°F (60°C) can harm your engine. A higher-rated thermostat can lead to overheating, while a lower-rated one can cause the engine to run too cool, impairing combustion efficiency and promoting carbon buildup.
Does this thermostat fit both V6 and V8 Verado models?
Yes, this part is designed for the newer generation of Mercury Verado engines, covering both the 3.4L V6 and 4.6L V8 platforms from 2018 to present, as detailed in the compatibility table. Always confirm your engine's serial number falls within the specified range.
How does the "self-cleaning" feature work?
The thermostat is engineered to allow small amounts of water and contaminants to pass through even when closed. This constant micro-flushing helps prevent sediment and salt buildup on the closing surfaces, ensuring the thermostat opens and closes reliably throughout its service life.
How often should I replace my engine's thermostat?
While there is no fixed replacement interval, it is considered a preventative maintenance item. Many technicians recommend replacing thermostats every 2-3 years, especially in saltwater environments, or whenever the water pump impeller is serviced to ensure cooling system reliability.
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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