Thermostat – Fits Mercury Marine 75-175 HP DFI (Replaces 833072, 833072002, 833072003, 833072004)
Thermostat – Fits Mercury Marine 75-175 HP DFI (Replaces 833072, 833072002, 833072003, 833072004) 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 – Fits Mercury Marine 75-175 HP DFI (Replaces 833072, 83...
Thermostat – Fits Mercury Marine 75-175 HP DFI (Replaces 833072, 833072002, 833072003, 833072004) is backordered and will ship as soon as it is back in stock.
Product Details
This Thermostat – Fits Mercury Marine 75-175 HP DFI Outboard Motors (Replaces 833072, 833072002, 833072003, 833072004) is designed for a wide range of Mercury Marine DFI 2-Stroke outboards from 1998 and newer. It is compatible with 1.5L 3-cylinder engines (75-115 HP) and 2.5L V6 engines (135-175 HP).
This component serves as a direct interchange for Mercury part numbers 833072, 833072002, 833072003, 833072004, and Sierra 18-3536.
- Installs as a direct replacement for the original part.
- Regulates engine temperature at a consistent 143°F (61.6°C).
- Requires thermostat seal 27-887978 for installation (sold separately).
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 833072 |
| Mercury | 833072002 |
| Mercury | 833072003 |
| Mercury | 833072004 |
| Sierra | 18-3536 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This thermostat fits specific Mercury Marine DFI and Optimax outboard models. Please verify your engine's serial number range for an exact match.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 1.5L 3-Cyl DFI | 75 | 2-Stroke | 2006–Up (0T980000-Up) | 833072003 | |
| Mercury | 1.5L 3-Cyl DFI | 90 | 2-Stroke | 2004–Up (0T801000-Up) | 833072003 | |
| Mercury | 1.5L 3-Cyl DFI | 115 | 2-Stroke | 2004–Up (0T801000-Up) | 833072003 | |
| Mercury | 2.5L V135 DFI | 135 | 2-Stroke | 1998–Up (0G590000-Up) | 833072003 | |
| Mercury | 2.5L V150 DFI | 150 | 2-Stroke | 1998–Up (0G590000-Up) | 833072003 | |
| Mercury | 2.5L V175 DFI | 175 | 2-Stroke | 2001–Up (0T178500-Up) | 833072003 | |
| Mercury | Optimax | 135-200 | 2-Stroke | 1998–Up | 833072003 |
Technical Specs
- Product Type
- Engine Thermostat
- Installation
- Direct Replacement
- Housing Color
- Silver/Metallic
- Operating Temperature
- 143°F (61.6°C)
- Other Technical Attributes
- Requires thermostat seal 27-887978 (not included)
What’s in the Box
- 1 x Thermostat (833072/833072002/833072003/833072004)
Installation Notes
- Disconnect the battery before beginning work.
- Allow the engine to cool completely and drain the cooling system.
- Locate the thermostat housing on the engine block.
- Remove the bolts securing the housing cover.
- Remove the old thermostat and its seal. Note the orientation of the thermostat.
- Thoroughly clean the mating surfaces of the housing and cover.
- Install the new thermostat in the correct orientation.
- Install a new thermostat seal (part no. 27-887978, sold separately).
- Reinstall the housing cover and tighten bolts to the manufacturer's specified torque.
- Refill the cooling system with the appropriate coolant.
- Reconnect the battery, start the engine, and check for leaks as it comes up to temperature.
Troubleshooting & FAQ
How do I know if my thermostat has failed?
Common signs of a faulty thermostat include the engine overheating at various speeds, running too cold (not reaching operating temperature), or erratic temperature gauge readings. A stuck-open thermostat will prevent the engine from warming up, while a stuck-closed one will cause rapid overheating.
Is the thermostat seal included?
No, the required thermostat seal (Mercury part number 27-887978) is not included with this thermostat and must be purchased separately to ensure a proper, leak-free installation.
Will this fit my Optimax engine?
This thermostat fits many Mercury Optimax models from 135 to 200 HP, manufactured from 1998 onwards. However, it is critical to consult your engine’s service manual or verify the OEM part number for your specific model and serial number to guarantee compatibility.
What is the correct operating temperature?
This thermostat is designed to open at 143°F (61.6°C), allowing coolant to circulate and maintain the engine within its optimal temperature range for performance and efficiency.
How often should I replace an outboard thermostat?
For preventative maintenance, it is good practice to inspect the thermostat annually and consider replacement every 2-3 years, or as recommended by your engine's manufacturer. Replacement is especially important if the boat is used in saltwater environments, which can accelerate corrosion.
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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