Thermostat (130°F/54°C) – Fits Mercury/Mariner 200-250 HP 3.0L EFI/DFI (Replaces 885599004, 8M0057307)
Thermostat (130°F/54°C) – Fits Mercury/Mariner 200-250 HP 3.0L EFI/DFI (Replaces 885599004, 8M0057307) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Thermostat (130°F/54°C) – Fits Mercury/Mariner 200-250 HP 3.0L EFI/...
Thermostat (130°F/54°C) – Fits Mercury/Mariner 200-250 HP 3.0L EFI/DFI (Replaces 885599004, 8M0057307) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Thermostat (130°F/54°C) – Fits Mercury/Mariner 200-250 HP 3.0L EFI/DFI is designed for a broad range of Mercury and Mariner engines from 1997 to 2008. It covers 3.0L V6 models, including both 2-Stroke DFI and 4-Stroke EFI variants, ensuring your engine maintains the correct operating temperature for optimal performance and longevity.
It serves as a direct replacement for Mercury OEM parts 885599003, 885599004, and 8M0057307, as well as aftermarket references Sierra 18-3535 and WSM 775-15.
- Engineered for direct OEM replacement fitment.
- Regulates engine temperature by opening at 130°F (54°C).
- Critical for preventing engine overheating and ensuring efficient operation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Mercury | 885599003 |
| Mercury | 885599004 |
| Mercury | 8M0057307 |
| Sierra | 18-3535 |
| WSM | 775-15 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This thermostat fits a wide array of V6 outboards under the Mercury and Mariner brands, particularly the 3.0L DFI and EFI platforms.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 200 DFI 3.0L (serial OG386496-Up) | 200 | 2-Stroke | 1997–Up | 885599003, 885599004, 8M0057307 | |
| Mercury | 200 3.0L DFI DTS | 200 | 2-Stroke | All | 885599003, 885599004, 8M0057307 | |
| Mercury | 200 3.0L EFI (serial OT750164-Up) | 200 | 4-Stroke | 2003–Up | 885599003, 885599004, 8M0057307 | |
| Mercury | 225 HP 3.0L Carb & EFI (serial OD280813-Up) | 225 | 4-Stroke | 1999–Up | 885599003, 885599004, 8M0057307 | |
| Mercury | 225 DFI (serial OG129222-Up) | 225 | 2-Stroke | 1998–Up | 885599003, 885599004, 8M0057307 | |
| Mercury | 225 3.0L EFI SeaPro (serial OT801000-Up) | 225 | 4-Stroke | 2004–Up | 885599003, 885599004, 8M0057307 | |
| Mercury | 225 3.0L DFI DTS (serial OT599000-Up) | 225 | 2-Stroke | 2003–Up | 885599003, 885599004, 8M0057307 | |
| Mercury | 250 3.0L EFI (serial OG760300-Up) | 250 | 4-Stroke | 1999–Up | 885599003, 885599004, 8M0057307 | |
| Mercury | 250 Long 3.0L EFI (serial OT861319-Up) | 250 | 4-Stroke | 2006–2008 | 885599003, 885599004, 8M0057307 | |
| Mercury | 225XS / Sport XS / Pro XS | 225 | 2-Stroke | 2002–2010 | 885599003, 885599004, 8M0057307 | |
| Mercury | 250XS / Sport XS / Pro XS | 250 | 2-Stroke | 2002–2014 | 885599003, 885599004, 8M0057307 |
Technical Specs
- Product Type
- Engine Thermostat
- Installation
- Direct OEM Replacement
- Operating Temperature
- 130°F (54°C) open temperature
- Warranty
- Typically 1 year (aftermarket)
What’s in the Box
- 1 x Thermostat (885599004/8M0057307)
Installation Notes
- Ensure the engine is off and cool, and disconnect the battery.
- Locate the thermostat housing on the engine block or cylinder head.
- Place a drain pan beneath the housing to catch any spilled coolant.
- Carefully remove the bolts securing the thermostat housing cover.
- Note the orientation of the old thermostat before removing it. The spring side typically faces the engine block.
- Clean the mating surfaces of both the housing and its cover, removing any old gasket material.
- Install the new thermostat, ensuring it is seated correctly, matching the original orientation.
- Install a new gasket (sold separately) and replace the housing cover.
- Tighten the housing bolts evenly to the manufacturer's recommended torque specification.
- Reconnect the battery, refill coolant if necessary, and run the engine to check for leaks and proper temperature regulation.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs of a faulty thermostat include the engine overheating at low speeds, the temperature gauge reading higher or lower than normal, or the engine failing to reach its proper operating temperature after warming up. An inconsistent temperature gauge can also indicate a thermostat that is stuck open or closed.
Does this thermostat come with a gasket?
No, a gasket is not included with this thermostat. We recommend purchasing a new gasket to ensure a proper seal during installation. Reusing an old gasket may lead to leaks.
Will this fit both 2-stroke and 4-stroke engines?
Yes, this thermostat is designed for a range of both 2-stroke DFI and 4-stroke EFI Mercury/Mariner 3.0L engines. Please refer to the detailed Engine & Model Compatibility table to confirm fitment for your specific model and year.
What is the correct operating temperature for this thermostat?
This thermostat is designed to open at 130°F (54°C), which helps regulate your engine's temperature to the optimal range specified by the manufacturer for performance and fuel efficiency.
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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