Thermostat Assembly for Mercury/Mariner 75–115 HP EFI and 150 EFI 4-Stroke Outboards – Replaces 892864T06, 8M0090819, 892864A06
Thermostat Assembly for Mercury/Mariner 75–115 HP EFI and 150 EFI 4-Stroke Outboards – Replaces 892864T06, 8M0090819, 892864A06 is backordered and will ship as soon as it is back in stock.
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Thermostat Assembly for Mercury/Mariner 75–115 HP EFI and 150 EFI 4...
Thermostat Assembly for Mercury/Mariner 75–115 HP EFI and 150 EFI 4-Stroke Outboards – Replaces 892864T06, 8M0090819, 892864A06 is backordered and will ship as soon as it is back in stock.
Product Details
This thermostat assembly is a direct-fit replacement for selected Mercury and Mariner 4-stroke EFI outboards. The company application data identifies it for 75–115 HP EFI and 150 EFI models. It is supplied as a single thermostat assembly, not as a multi-piece thermostat kit with a separate housing, O-ring, or clamp.
The thermostat regulates engine cooling-system temperature and is rated at approximately 50°C (122°F). Always confirm the required thermostat temperature, engine model, and serial number in the owner's or service manual before installation.
- Replacement thermostat assembly for selected Mercury/Mariner EFI 4-stroke outboards.
- Customer-facing OEM references include Mercury 892864T06, 8M0090819, and 892864A06.
- Cross-references include Sierra 18-3635 and 18-3633.
- Sold as one thermostat assembly; additional housing or sealing components are not specified as included for this product.
Part Number Matrix
Use these references to compare the thermostat required for your engine. Part-number references do not replace model and serial-number verification.
| Brand | Part Number | Reference Type | Notes |
|---|---|---|---|
| Mercury | 892864T06 | OEM reference | Thermostat reference for the listed EFI applications. |
| Mercury | 8M0090819 | OEM reference | Quicksilver/Mercury thermostat assembly reference. |
| Mercury | 892864A06 | OEM reference | Additional company-listed Mercury reference. |
| Sierra | 18-3635 | Aftermarket cross-reference | Thermostat reference. |
| Sierra | 18-3633 | Aftermarket cross-reference | Thermostat reference. |
Engine & Model Compatibility
Fitment depends on the complete engine application, including horsepower, stroke, model, and serial number. The following conditions should be treated together when checking compatibility.
| Brand | Model/Application | Rated HP | Stroke | Serial Condition | Reference |
|---|---|---|---|---|---|
| Mercury/Mariner | EFI outboard | 75–115 HP | 4-Stroke | 1B366823 through 2B094995 | 892864T06 / 8M0090819 |
| Mercury/Mariner | EFI outboard | 150 HP | 4-Stroke | 1B905505 and up | 8M0090819 |
Some catalogs distinguish between thermostat-only and thermostat-with-housing applications. Verify the original component and the exact engine serial number before ordering.
Technical Specifications
- Product Type
- Thermostat assembly
- Application
- Mercury/Mariner EFI 4-stroke outboards
- Rated Temperature
- Approximately 50°C (122°F)
- Product Configuration
- Single thermostat assembly
- Installation
- Direct-fit replacement when the application and serial number match
- Fuel Type
- Gasoline outboard application
What’s in the Box
- 1 x Thermostat assembly
A housing, O-ring, clamp, gasket, or other installation hardware is not identified as included in the company package data. Reuse or replacement of surrounding components should be determined from the engine service manual and the condition of the original parts.
Installation Notes
- Confirm the engine model, horsepower, stroke, and serial number before beginning work.
- Allow the engine to cool completely and follow the service manual's cooling-system safety procedure.
- Disconnect the battery if required by the manufacturer's service instructions.
- Locate the thermostat according to the engine service manual and remove the required cover or housing components.
- Note the orientation of the original thermostat before removal.
- Clean the sealing surfaces and inspect the housing, fasteners, gasket, and O-ring for damage or corrosion.
- Install the replacement thermostat in the specified orientation.
- Install any required gasket or seal specified by the engine service manual; these items are not identified as included with this single thermostat assembly.
- Reinstall the cover or housing and tighten fasteners to the manufacturer's specified torque.
- Restore the cooling system as required, start the engine, and check for leaks and proper operating temperature.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Possible symptoms include overheating, an engine that runs below its normal operating temperature, unstable temperature readings, or cooling-system leakage near the thermostat cover. Diagnose the cooling system using the engine service manual before replacing parts.
Will this fit an engine that is not listed?
Do not assume fitment from horsepower alone. Match the engine brand, model, stroke, horsepower, and serial number to the applicable catalog or service-manual information. If those details do not match, select a different verified application.
What temperature is this thermostat?
The company data identifies this application as approximately 50°C (122°F). Use only the temperature rating specified for your particular engine in its owner's or service manual.
Does this include the thermostat housing, O-ring, and clamp?
No complete kit contents are specified for this product. The company record identifies it as a single thermostat assembly, so a housing, O-ring, clamp, gasket, or other hardware should not be assumed to be included.
Can I reuse the old housing or seal?
Inspect those parts and follow the engine service manual. Replace any worn, damaged, corroded, or hardened sealing components before returning the engine to service.
Is this an OEM part?
This listing is for a replacement thermostat assembly. Mercury OEM reference numbers are provided for identification and fitment comparison; the replacement should not be represented as a genuine Mercury-branded part unless the physical part and packaging are specifically identified as genuine OEM.
When should the thermostat be replaced?
Inspect and service the thermostat according to the engine manufacturer's maintenance schedule. Replacement may also be appropriate when the thermostat is sticking, corroded, damaged, or associated with abnormal engine temperature.
Shipping speed and cost
Shipping methods, delivery estimates, and available costs are shown at checkout and may vary by destination.
Warranty and returns
Warranty and return eligibility are governed by the applicable store policies. Contact customer support with your order details before returning a product.
Safety & Important Information
- Verify the engine model, year when applicable, horsepower, stroke, and serial number before purchase.
- Use only the thermostat temperature specified for the engine.
- Do not operate the engine if the thermostat cover leaks or the temperature remains abnormal after installation.
- Professional installation is recommended when the required service procedure or torque specifications are unknown.
About Sea Sierra
- Marine Parts Support — We provide replacement components for common marine maintenance and repair applications.
- Fitment-Focused Information — Model, serial, and part-number references are presented to help customers verify compatibility.
- Global Fulfillment — Available shipping methods and delivery estimates are presented during checkout.
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