Thermostat for Mercury Mariner Verado 135–300 HP – Replaces Mercury 892864T04, 8M0174561 and Sierra 18-3631-K
Thermostat for Mercury Mariner Verado 135–300 HP – Replaces Mercury 892864T04, 8M0174561 and Sierra 18-3631-K is backordered and will ship as soon as it is back in stock.
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Thermostat for Mercury Mariner Verado 135–300 HP – Replaces Mercury...
Thermostat for Mercury Mariner Verado 135–300 HP – Replaces Mercury 892864T04, 8M0174561 and Sierra 18-3631-K is backordered and will ship as soon as it is back in stock.
Product Details
This thermostat for Mercury and Mariner Verado outboard engines is listed for 135–300 HP Verado applications. It helps regulate engine operating temperature by controlling when cooling flow begins through the thermostat system.
The thermostat is listed as a replacement for Mercury part numbers 892864T04 and 8M0174561. The corresponding Sierra reference listed for this product is 18-3631-K.
- Application range: Mercury and Mariner Verado 135–300 HP.
- Nominal opening temperature: 143°F (62°C).
- Aftermarket replacement thermostat for the listed applications.
- Verify the engine model, serial number and original part number before ordering.
Part Number Matrix
Use the following manufacturer and aftermarket references to help identify the correct replacement.
| Brand | Part Number | Reference Type |
|---|---|---|
| Mercury | 892864T04 | OEM reference |
| Mercury | 8M0174561 | OEM reference |
| Sierra | 18-3631-K | Aftermarket reference |
Engine & Model Compatibility
This product is listed for Mercury and Mariner Verado engines rated from 135 HP through 300 HP. The available fitment information does not establish one universal fit for every year, serial-number range or engine configuration within that horsepower range.
| Brand | Model Family | Rated HP | Stroke | Fitment Condition | Applicable References |
|---|---|---|---|---|---|
| Mercury | Verado | 135–300 HP | Verify for your engine | Confirm model and serial number before purchase | 892864T04; 8M0174561 |
| Mariner | Verado | 135–300 HP | Verify for your engine | Confirm model and serial number before purchase | 892864T04; 8M0174561 |
Technical Specs
- Product Type
- Thermostat
- Application
- Mercury and Mariner Verado 135–300 HP outboard engines
- Nominal Opening Temperature
- 143°F (62°C)
- OEM References
- 892864T04; 8M0174561
- Aftermarket Reference
- Sierra 18-3631-K
- Installation
- Replacement installation; follow the engine service-manual procedure
What’s in the Box
This listing is for one thermostat. The company product record does not specify additional seals, clamps, housing components or other installation hardware as included. Confirm the contents of the package received before beginning service.
Installation Notes
- Turn the engine off, allow it to cool completely and follow all applicable marine-service safety procedures.
- Confirm the engine model, serial number and original thermostat reference before removing the existing part.
- Access the thermostat according to the engine manufacturer's service-manual instructions.
- Remove the original thermostat and inspect the housing, sealing surfaces and related components for corrosion, damage or debris.
- Install the replacement thermostat in the correct orientation and use any required seal or gasket specified by the service manual.
- Reassemble the thermostat area and tighten fasteners to the manufacturer's specified torque.
- Restore the cooling system as directed by the service manual, then run the engine using the proper water supply and check for leaks or abnormal temperature indications.
Troubleshooting & FAQ
What is the opening temperature of this thermostat?
The listed nominal opening temperature is 143°F (62°C).
Which engines is this thermostat intended for?
The company fitment record lists Mercury and Mariner Verado engines from 135 HP through 300 HP. Because fitment can vary by model and serial-number range, compare the original part number and confirm the engine details before ordering.
Is this a complete thermostat kit?
The company record identifies this SKU as a single product rather than a multi-piece kit. The supplied product information does not confirm that an O-ring, clamp, housing or other installation hardware is included.
What part numbers can this replace?
The listed references are Mercury 892864T04, Mercury 8M0174561 and Sierra 18-3631-K. These references should be treated as identification aids; verify the complete engine application before installation.
Is this an OEM part?
This listing is for an aftermarket replacement thermostat. Mercury part numbers are shown only as reference numbers for identification and compatibility checking.
Should installation be performed by a professional?
Thermostat service affects engine cooling. If you are not familiar with outboard cooling-system service, use a qualified marine technician and follow the applicable service-manual instructions.
Safety & Important Info
- Do not rely on horsepower alone to confirm fitment; check the complete engine model, serial number and original part number.
- Do not operate the engine without the proper cooling-water supply and appropriate service precautions.
- Inspect related seals and housing components during installation. Any replacement parts required beyond the thermostat are not confirmed as included with this listing.
- This is an aftermarket replacement component, not a Mercury OEM part.
About Sea Sierra
- Marine Replacement Parts — We supply replacement components for common marine service applications.
- Application-Focused Listings — Product references and fitment information are provided to help customers compare their original parts.
- Service-Minded Support — Verify your engine details before ordering and consult a qualified technician when installation requirements are uncertain.
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