Thermostat & Gasket Kit for Mercury Marine 8–35 HP 4-Stroke Outboards – Replaces 855676002 and 8M0119207
Thermostat & Gasket Kit for Mercury Marine 8–35 HP 4-Stroke Outboards – Replaces 855676002 and 8M0119207 is backordered and will ship as soon as it is back in stock.
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Thermostat & Gasket Kit for Mercury Marine 8–35 HP 4-Stroke Out...
Thermostat & Gasket Kit for Mercury Marine 8–35 HP 4-Stroke Outboards – Replaces 855676002 and 8M0119207 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket thermostat and gasket kit is intended for selected Mercury Marine 8–35 HP 4-Stroke outboard motors and replaces the listed Mercury reference numbers. The supplied application information covers selected 209cc two-cylinder and three-cylinder engines, including certain Mercury, Tohatsu, and Nissan 4-Stroke models that use a 60°C (140°F) thermostat.
Because fitment can vary by model designation, production year, engine configuration, and serial number, compare the part number and application details with your original component before ordering. The references below are provided for identification and interchange checking; they do not replace confirmation against the specific engine serial number.
- Replacement thermostat service kit for selected marine 4-Stroke applications.
- 60°C (140°F) thermostat rating.
- Includes the thermostat, thermostat-cover gasket, and rubber ring seal listed below.
- Designed as an aftermarket direct-replacement solution where the listed references and fitment conditions match.
Part Number Matrix
Use the following manufacturer and aftermarket references to help compare your existing part.
| Brand | Part Number |
|---|---|
| Mercury | 855676002 |
| Mercury | 8M0119207 |
| Mercury | 8M0139434 |
| Mercury | 855676005 |
| Sierra | 18-43175 |
| Mallory | 9-43175 |
| Tohatsu | 3NV010300M |
| Tohatsu | 3R3-01030-0 |
| Tohatsu | 3R3010300M |
Engine & Model Compatibility
The applications below reflect the supplied fitment information. Confirm the complete model, year, stroke, configuration, and serial-number range before installation.
| Brand | Model or Configuration | Rated HP | Stroke | Years | Applicable Reference | Serial or Application Notes |
|---|---|---|---|---|---|---|
| Mercury | 4-Stroke | 8 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Serial R042475 and up |
| Mercury | 4-Stroke | 9.9 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Serial R042475 and up |
| Mercury | Carbureted, 2-cylinder | 15 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Serial R235949 and up |
| Mercury | SeaPro | 15 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Serial R051685 and up |
| Mercury | Carbureted, 2-cylinder | 20 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Serial R235168 and up |
| Mercury | EFI, 3-cylinder | 25 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Serial R106999 and up |
| Mercury | Jet EFI, 3-cylinder | 25 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Serial R165086 and up |
| Mercury | SeaPro | 25 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Serial R051710 and up |
| Mercury | EFI, 3-cylinder | 30 | 4-Stroke | 2005–2012 | 855676002 / 8M0119207 | Serial T409000–1B226999 |
| Mercury | SeaPro | 30 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Selected 209cc models |
| Mercury | Various | 35 | 4-Stroke | 2005–present | 855676002 / 8M0119207 | Selected 209cc models |
| Tohatsu | Various listed applications | 8–30 | 4-Stroke | Not specified | 3NV010300M / 3R3-01030-0 | Verify the exact model and serial number |
Technical Specifications
- Product Type
- Thermostat and gasket kit
- Thermostat Rating
- 60°C (140°F)
- Application
- Selected Mercury Marine, Tohatsu, and Nissan 4-Stroke outboards
- Installation
- Replacement installation; verify the application before fitting
- Product Status
- Aftermarket replacement, not an OEM-branded component
What’s in the Box
- 1 × 60°C (140°F) thermostat, replacing the listed 855676002 / 8M0119207 references
- 1 × thermostat-cover gasket, listed as replacing 27-853702005
- 1 × rubber ring seal
Installation Notes
- Confirm the engine model, stroke, horsepower, year, serial number, and existing thermostat reference before starting.
- Switch off the engine and allow it to cool completely.
- Follow the engine manufacturer’s service procedure for access to the thermostat housing.
- Remove the thermostat cover and note the orientation of the original thermostat, gasket, and seal.
- Remove all old sealing material and clean the mating surfaces without damaging the housing or cover.
- Install the replacement thermostat, gasket, and rubber ring seal in the correct orientation.
- Reinstall the cover and tighten the fasteners to the manufacturer’s specified torque.
- Operate the engine using the appropriate water-supply or test procedure for the outboard.
- Check for leakage and confirm that the engine reaches and maintains its normal operating temperature.
Installation should be performed by a qualified technician when the correct service procedure, torque values, or cooling-system requirements are not known. Do not add automotive coolant or drain a closed cooling system unless the specific engine design and manufacturer’s service instructions require it.
Troubleshooting & FAQ
How do I confirm that this kit fits my engine?
Match the thermostat or kit reference on your existing part with the Part Number Matrix, then confirm the complete engine model, horsepower, stroke, year, configuration, and serial-number range. A model that falls within the general horsepower range is not sufficient by itself.
What are common signs of a failing thermostat?
Possible symptoms include overheating, the engine running below its normal operating temperature, unstable temperature readings, or leakage near the thermostat housing. Before replacing the thermostat, inspect the water passages, water pump, cooling-system components, and temperature-sensing equipment as appropriate.
Is this a 140°F or 60°C thermostat?
It is specified as a 60°C thermostat, which is approximately 140°F.
How often should the thermostat be replaced?
There is no single replacement interval for every outboard. Inspect the thermostat during scheduled cooling-system service and replace it if it is corroded, sticking, damaged, contaminated, or associated with abnormal engine temperature.
Is this an OEM part?
No. This listing is for an aftermarket replacement kit intended for applications where the listed reference numbers and fitment conditions match. Mercury, Tohatsu, Nissan, Sierra, and Mallory names and numbers are used only to identify compatibility or reference applications.
What should I do if my model appears compatible but the part looks different?
Do not install the part until the dimensions, housing arrangement, thermostat rating, gasket shape, and reference number have been confirmed. Contact a qualified marine technician or compare the engine serial number with the manufacturer’s parts information.
Safety & Important Information
- Work only on a completely cool engine and follow the engine manufacturer’s service instructions.
- Verify fitment using the complete model and serial-number information before ordering or installing.
- Do not force the thermostat, gasket, or seal into position; incorrect orientation can cause leakage or cooling problems.
- This is an aftermarket replacement and is not an OEM-branded component.
- Professional installation is recommended when the correct service procedure or torque specifications are unavailable.
About Sea Sierra
- Marine Parts Focus — Replacement components selected for common marine service applications.
- Application-Conscious Listings — Use the listed references and engine conditions to confirm compatibility before purchase.
- Support for Routine Maintenance — Replacement parts for keeping compatible outboard cooling systems in service.
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