Mercury Outboard Thermostat 120°F – 8M0117413
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You have 30 days to request a return. All sale items are final sale.
The Mercury / Quicksilver 8M0117413 Thermostat is a genuine OEM 120°F (48.8°C) thermostat used on small-to-mid horsepower Mercury 4-stroke outboards.
This thermostat regulates engine temperature in raw water cooled systems, allowing the engine to warm up quickly while preventing overheating under load. The lower 120°F rating is specific to these engines and is required for proper fuel mapping, combustion efficiency, and corrosion control.
It uses a wax-element valve that opens progressively with temperature, ensuring stable cooling performance across idle and high RPM operation. Built to OEM standards, it provides reliable operation in both freshwater and saltwater environments.
Key Features
- Genuine Mercury / Quicksilver OEM part
- 120°F (48.8°C) temperature rating
- Designed for raw water cooled outboards
- Maintains proper operating temperature
- Prevents overheating and cold-running issues
- Corrosion-resistant construction
- Direct OEM replacement
Engine Compatibility
Mercury / Mariner 4-Stroke Outboards
Fits:
- 35 HP EFI (4-stroke)
- 40 HP EFI (4-stroke)
- 50 HP EFI (4-stroke)
- 60 HP EFI (4-stroke)
➡️ Typically applies to engines:
- Serial range: 1C453840 and newer
➡️ Common on:
- Mercury 4-cylinder EFI platforms
- SeaPro variants in same HP range
Important Fitment Notes
- ✔ Raw water cooled systems only
- ✔ Must match OEM temp rating (120°F)
- ❌ Not interchangeable with 140° / 160° thermostats
- ✔ Superseded by 8M0168892 (updated design)
Specifications
- Part Number: 8M0117413
- Superseded By: 8M0168892
- Temperature Rating: 120°F (48.8°C)
- Type: Engine thermostat
- Cooling System: Raw water cooled
- Operation: Wax-element valve
What’s Included
- Thermostat (gasket/seal sold separately unless specified)
When This Part Needs Replacement
- Engine overheating
- Engine running too cold
- Temperature fluctuation
- Debris or corrosion causing sticking
- Routine service interval
Installation Notes
- Install with correct orientation (spring toward engine)
- Inspect and replace seals/gaskets
- Check cooling passages for debris
- Verify operating temperature after install
Alternate / Superseded Part Numbers
OEM Cross References
- Mercury / Quicksilver: 8M0117413
- Supersedes to: 8M0168892
- Sierra: 18-3640
Shipping
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
💡 Parts Desk Insight
These smaller EFI Mercs are very sensitive to thermostat temp—installing the wrong rating (like 140°) will throw off fuel mapping and cause poor performance 👍
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.