Aftermarket 143°F Thermostat for Mercury Marine DFI Outboards 110–200 HP – Replaces 833072003

Product Details

This aftermarket 143°F engine thermostat is designed as a replacement for select Mercury Marine DFI 2-stroke outboard applications. It helps regulate engine operating temperature for consistent cooling-system performance and is identified in Mercury parts catalogs as a 62°C (143°F) thermostat.

The primary Mercury Marine reference is 833072003. Sierra reference 18-3536 is documented as replacing this number. Always verify the complete engine model and serial-number range before ordering because similar Mercury engines may use different thermostat references.

• Aftermarket replacement thermostat for selected Mercury Marine DFI outboards.
• Nominal operating temperature: 143°F (62°C).
• Designed for direct replacement when the original part number and application match.
• Thermostat only; seals, gaskets, housings, and other service parts are not confirmed as included.

Part Number Matrix

These references are shown for identification and interchange checking. They should not be treated as universal substitutes for every engine application.

Engine & Model Compatibility

The catalog relationships below retain the engine model, horsepower, stroke family, and serial-number conditions together. A model name or horsepower alone is not sufficient for fitment confirmation.

Important: Some aftermarket catalogs associate related thermostat numbers with additional 75–115 HP or larger Optimax applications. Those relationships are not automatically interchangeable with this 833072003 replacement. Confirm the exact OEM number and serial range on your engine before purchase.

Technical Specifications

Product Type

Engine thermostat

Operating Temperature

143°F (62°C)

Application

Selected Mercury Marine DFI 2-stroke outboards

Installation

Direct replacement when the original part number and engine application match

Primary OEM Reference

Mercury Marine 833072003

Aftermarket Reference

Sierra 18-3536

What's in the Box

• 1 x Engine thermostat

Seal or gasket inclusion is not confirmed for this item. Inspect the old seal and consult the engine service information to determine whether a new seal is required for installation.

Installation Notes

1. Allow the outboard to cool completely and follow all applicable service and safety procedures.
2. Disconnect the battery or observe the manufacturer's electrical-safety procedure before beginning service.
3. Locate the thermostat housing and note the orientation of the original thermostat.
4. Remove the housing fasteners and carefully remove the cover.
5. Remove the old thermostat and seal. Clean the mating surfaces without damaging the housing.
6. Install the replacement thermostat in the correct orientation. Use a new seal or gasket if required by the service manual.
7. Reinstall the housing and tighten the fasteners to the manufacturer's specified torque.
8. Run the engine according to the service procedure and check for leaks, proper water flow, and normal operating temperature.
9. Stop operation immediately if the engine overheats or if cooling-system leakage is detected.

Troubleshooting & FAQ

Safety & Important Information

• Verify the OEM reference, engine model, horsepower, stroke, and serial-number range before purchase.
• Do not rely on a general horsepower range when the part number or serial range differs.
• Allow the engine to cool before opening the thermostat housing.
• Follow the manufacturer's service manual for torque values, seal requirements, and cooling-system checks.
• This is an aftermarket replacement and is not manufactured by Mercury Marine or Sierra.

About Sea Sierra

• Marine Replacement Parts — Practical replacement components for maintenance and repair applications.
• Application-Focused Information — Use OEM references and serial-number conditions to help verify fitment.
• Support for Maintenance — Consult the engine service manual whenever installation requirements or included service parts are uncertain.