Mercury Outboard 140°F Thermostat - 8M0119207
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The Mercury Quicksilver 8M0119207 is a genuine Mercury Marine OEM 140°F / 60°C thermostat used in select Mercury, Mariner, and SeaPro outboard cooling systems. The thermostat regulates cooling-water flow through the engine by opening at the specified temperature, helping the outboard warm up properly and maintain the correct operating range during use.
This thermostat should be matched by exact outboard serial number, horsepower, thermostat housing layout, and Mercury parts diagram before ordering.
Key Features
- Genuine Mercury Marine OEM thermostat.
- Mercury/Quicksilver part number: 8M0119207.
- Operating temperature: 140°F / 60°C.
- UPC reference: 745061624085.
- Used in select small-to-midrange Mercury, Mariner, and SeaPro outboard cooling systems.
- Helps regulate engine temperature and cooling-water flow.
- Important replacement part for overheating, cold-running, slow warm-up, unstable temperature, or stuck-thermostat symptoms.
- Supersedes earlier Mercury thermostat references in supported applications.
- Related gasket reference supplied: 27-853702005 — verify by serial number and thermostat housing diagram.
Engine Compatibility
Common application context includes select Mercury and Mariner outboards where the factory cooling-system diagram calls for 8M0119207, including:
- Select 8 HP and 9.9 HP FourStroke 209cc applications where specified.
- Select 15 HP and 20 HP carbureted FourStroke applications where specified.
- Select 25 HP and 30 HP EFI FourStroke applications where specified.
- Select Jet and SeaPro configurations where the Mercury parts diagram confirms this thermostat.
- Common serial-number references include 0R042475 and higher, 0R235949 through 0R833819, and 0R106999 and higher, depending on horsepower and engine family.
Use this thermostat only where the Mercury parts diagram or service manual specifically calls for 8M0119207.
Serial Number Fitment Notice
Confirm fitment by outboard serial number, horsepower, model family, cooling-system configuration, thermostat housing style, gasket type, and required opening temperature before ordering. Similar Mercury portable outboards can use different thermostats depending on production range, EFI/carbureted configuration, SeaPro or standard model setup, and thermostat housing design.
Do not substitute a different temperature rating unless the Mercury service manual specifically calls for it.
When This Part Needs Replacement
Replace the thermostat if the engine runs too cold, overheats, takes too long to warm up, has unstable operating temperature, shows weak temperature regulation, or fails thermostat testing. Replacement is also recommended during cooling-system service if the thermostat is corroded, scaled, stuck open, stuck closed, physically damaged, or removed from the housing during repair.
Installation Notes
Drain or lower the cooling water level as required before removing the thermostat housing. Clean the thermostat seat and housing surfaces carefully, then replace the gasket or seal shown in the Mercury parts diagram. Do not reuse a compressed, torn, swollen, or hardened gasket.
Install the thermostat in the correct orientation and tighten the housing bolts to the Mercury service-manual specification for the exact engine. After installation, run the outboard on a proper water supply and confirm stable temperature control, strong cooling-water flow, and no leaks around the thermostat housing.
Alternate/Superseded Part Numbers
- 8M0119207 — current Mercury/Quicksilver OEM thermostat part number
- 855676002 — earlier Mercury reference; verify by serial number and diagram
- 855676005 — earlier Mercury reference; verify by serial number and diagram
- 745061624085 — UPC reference
- 27-853702005 — related thermostat gasket reference supplied; verify by diagram before ordering
Related Service Parts
Thermostat service may also require the matching thermostat gasket, housing seal, housing cover hardware, cooling-system inspection parts, and water pump service parts depending on the engine condition. Confirm all related parts by outboard serial number before ordering.
Parts Desk Insight
A thermostat that is stuck open can make an outboard run too cold, idle poorly, or build carbon because the engine never reaches its designed operating range. A thermostat that is stuck closed can cause overheating and serious engine damage. Match the thermostat by serial number and temperature rating, then replace the housing gasket during the same service.
Shipping: Ships same or next day for fast Canada wide shipping. ⚓
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.
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