Mercury Outboard Thermostat 140°F – 8M0162139
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You have 30 days to request a return. All sale items are final sale.
The Mercury / Quicksilver 8M0162139 Thermostat is a genuine OEM 140°F (60°C) thermostat designed for modern Mercury outboard engines.
This thermostat controls coolant flow through the engine, allowing it to warm up quickly and maintain a stable operating temperature under load. The 140°F calibration is specifically engineered for high-output outboard applications where lower operating temperatures are required for durability and performance.
It features a self-cleaning valve design, allowing debris and contaminants in the cooling system to pass through without sticking the thermostat closed. Combined with corrosion-resistant materials, this ensures long service life in saltwater environments.
Key Features
- Genuine Mercury / Quicksilver OEM part
- 140°F (60°C) temperature rating
- Designed for modern 4-stroke outboards
- Self-cleaning valve reduces sticking/failure
- Corrosion-resistant construction for saltwater use
- Maintains proper engine temperature and efficiency
- Direct OEM replacement
Engine Compatibility
Mercury 4-Stroke Outboards (Serial-Specific)
Fits engines including:
- 175 HP V6 (3.4L)
- 200 HP V6 (3.4L)
- 225 HP V6 (3.4L)
- 250 HP V8 (4.6L)
- 300 HP V8 (4.6L)
- 300R / 450R Racing models
➡️ Applies to engines with serial numbers:
- 2B529482 and newer
Important Fitment Notes
- ✔ Designed for modern Mercury 4-stroke outboards only
- ✔ Used in raw water cooling systems
- ❌ Not compatible with older carbureted or 2-stroke engines
- ❌ Not interchangeable with 160°F or 170°F thermostats
Specifications
- Part Number: 8M0162139
- Temperature Rating: 140°F (60°C)
- Type: Engine thermostat
- Operation: Wax-element valve
- Cooling System: Raw water cooled outboards
- Construction: Corrosion-resistant metal
What’s Included
- Thermostat only
(Seals/O-rings sold separately unless specified)
When This Part Needs Replacement
- Engine overheating
- Engine running too cold (thermostat stuck open)
- Temperature fluctuations
- Debris-related sticking or corrosion
- Routine service on high-hour outboards
Installation Notes
- Replace seals/O-rings at the same time
- Install with correct orientation
- Inspect cooling passages for debris
- Verify proper temp after install
Alternate / Superseded Part Numbers
OEM Cross References
- Mercury / Quicksilver: 8M0162139
- Replaces: 8M0137816
Shipping
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
💡 Parts Desk Insight
These newer Mercury thermostats rarely fail closed—most failures are debris-related sticking, so if you’re replacing one, it’s worth checking the whole cooling system 👍
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.