Thermostat Housing Kit – Fits Mercury/Mariner Verado 135-400 HP (Replaces 892864T04, 8M0174561)
Thermostat Housing Kit – Fits Mercury/Mariner Verado 135-400 HP (Replaces 892864T04, 8M0174561) is backordered and will ship as soon as it is back in stock.
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Thermostat Housing Kit – Fits Mercury/Mariner Verado 135-400 HP (Re...
Thermostat Housing Kit – Fits Mercury/Mariner Verado 135-400 HP (Replaces 892864T04, 8M0174561) is backordered and will ship as soon as it is back in stock.
Product Details
This Thermostat Housing Kit – Fits Mercury/Mariner Verado 135-400 HP (Replaces 892864T04, 8M0174561) is engineered for Mercury and Mariner Verado four-stroke outboard engines from 135 HP to 400 HP (2004–present). It ensures your engine maintains optimal operating temperature by precisely regulating coolant flow for peak performance and longevity.
This assembly is a direct replacement for Mercury part numbers 892864T04 and 8M0174561, as well as Sierra equivalents 18-3631 and 18-3631-K.
- Engineered for direct OEM replacement, ensuring a perfect fit and function.
- Includes the thermostat pre-seated within the housing for a simplified installation.
- Comes complete with the necessary O-ring seal to prevent coolant leaks.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Mercury | 892864T04 | 8M0174561 | Original OEM part number. |
| Mercury | 8M0174561 | Current OEM part number. | |
| Sierra | 18-3631 | Aftermarket cross-reference. | |
| Sierra | 18-3631-K | Aftermarket kit version. |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This part is designed specifically for the Mercury and Mariner Verado L4 and L6 engine platforms. Please verify your serial number against the notes provided in the table to ensure correct fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | Verado L4 | 135 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 4-cylinder models (1B227000-2B576734) |
| Mercury | Verado L4 | 150 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 4-cylinder models (1B227000-2B576734) |
| Mercury | Verado L4 | 175 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 4-cylinder models (1B227000-2B576734) |
| Mercury | Verado L4 | 200 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 4-cylinder models (1B517159-2B576734) |
| Mercury | Verado L6 | 200 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 6-cylinder models (0T980000-2B578935) |
| Mercury | Verado L6 Pro | 200 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | Pro 6-cylinder models (2B034840-2B577715) |
| Mercury | Verado L6 | 225 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 6-cylinder models (0T980000-2B578935) |
| Mercury | Verado L6 | 250 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 6-cylinder models (0T980000-2B578935) |
| Mercury | Verado L6 Pro | 250 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | Pro 6-cylinder models (1B830170-2B577715) |
| Mercury | Verado L6 | 275 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 6-cylinder models (0T980000-2B578935) |
| Mercury | Verado L6 | 300 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | 6-cylinder models (1B517434-2B578935) |
| Mercury | Verado L6 Pro | 300 | 4-Stroke | 2004–Present | 892864T04/8M0174561 | Pro 6-cylinder models (1B830170-2B577715) |
| Mercury | Verado L6 Pro | 350 | 4-Stroke | 2015–Present | 892864T04/8M0174561 | 2.6L L6 Pro models (2B141124-3B342962) |
| Mercury | Verado L6 | 350 | 4-Stroke | 2015–Present | 892864T04/8M0174561 | 2.6L L6 models (2B141617-3B342962) |
| Mercury | Verado L6 | 400 | 4-Stroke | 2016–Present | 892864T04/8M0174561 | 2.6L L6 models (2B618256-3B342962) |
| Mercury | Racing L6 | 400R | 4-Stroke | 2015–Present | 892864T04/8M0174561 | 2.6L L6 Racing models (2B141124-3B342962) |
Technical Specs
- Product Type
- Thermostat Housing Assembly
- Installation
- Direct OEM Replacement
- Connection
- Hose connection with clamp
- Housing Material
- Composite (OEM) or Metal Alloy (Aftermarket)
- Operating Temperature
- 140°F (60°C) nominal opening temperature
- Other Technical Attributes
- Includes thermostat pre-seated in housing, O-ring seal required for installation
- Warranty
- 1-year manufacturer warranty (varies by brand)
What’s in the Box
- 1 x Thermostat with Housing Assembly (Replaces 892864T04/8M0174561)
- 1 x O-Ring Seal (8M005958)
- 1 x Clamp (888988008) (Note: Included with some kits, but may require separate purchase)
Installation Notes
- Ensure the engine is off and completely cool. Disconnect the negative battery terminal.
- Place a drain pan under the engine and carefully drain the coolant from the system.
- Locate the thermostat housing and disconnect the attached coolant hoses.
- Remove the mounting bolts securing the old housing assembly and carefully lift it away from the engine block.
- Thoroughly clean the engine's mounting surface to remove any old gasket material or corrosion.
- Place the new O-ring seal onto the new thermostat housing assembly.
- Position the new assembly onto the engine block and tighten the mounting bolts to the manufacturer's specified torque.
- Reconnect the coolant hoses and secure them with clamps.
- Refill the cooling system with the appropriate coolant.
- Reconnect the battery, start the engine, and let it warm up, checking carefully for any leaks.
Troubleshooting & FAQ
What are the signs of a failing thermostat or housing?
Common symptoms include engine overheating, engine temperatures that are too low, erratic temperature gauge readings, or visible coolant leaks from the housing area.
How can I confirm this kit fits my specific Verado engine?
Verify your engine's model, horsepower, and year against our compatibility table. For precise confirmation, match your engine's serial number to the ranges listed in the 'Notes' column.
What is the difference between the OEM composite and aftermarket metal housings?
The original OEM housing is made of a durable composite material. Some aftermarket versions are made of a metal alloy. While metal can offer greater durability against impact, both materials are designed to perform to OEM cooling specifications.
Is the O-ring seal included with this kit?
Yes, a new O-ring seal is included and is critical for ensuring a leak-proof installation. Always use the new seal provided.
How often should a thermostat be replaced on a Verado?
As a preventive maintenance item, it is often recommended to inspect and potentially replace the thermostat every 300 service hours or every 3 years, whichever comes first, or if any cooling issues are suspected.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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