EMP Stainless Steel Thermostat 75-00403, Replaces 18-3543, Johnson/Evinrude Outboards

The EMP 75-00403 is a stainless steel thermostat engineered as a direct replacement for Johnson/Evinrude outboard engines. Stainless steel construction resists the corrosion and mineral buildup common in raw-water cooling systems, helping the thermostat maintain accurate opening temperature over repeated heat cycles. Correct thermostat function is critical to outboard engine health: it regulates coolant flow so the engine reaches and holds proper operating temperature, protecting against both overheating and the inefficient combustion that comes from running too cold. This thermostat is a straightforward maintenance-item replacement for engines showing symptoms of a failed or sticking thermostat, such as overheating alarms, erratic temperature gauge readings, or reduced performance. It cross-references directly to OEM part number 18-3543, making it easy to confirm fit against your existing part before ordering. The EMP 75-00403 is intended for outboard engines in the Johnson/Evinrude (OMC/BRP) lineup, including 200 HP (1977-83) and 235 HP (1978-85) applications. Keeping a spare on hand is good practice for seasonal maintenance or as an emergency replacement, since a failed thermostat can leave an engine unable to run safely at operating temperature.

Specifications

• Brand: EMP
• Manufacturer Part Number: 75-00403
• Product Name: Thermostat (Stainless Steel)
• Material: Stainless Steel
• Weight: 0.061 pounds
• UPC: 840080461175
• OEM Cross-Reference: 18-3543

Fitment

• Johnson/Evinrude (OMC/BRP) outboard, 200 HP, 1977-83
• Johnson/Evinrude (OMC/BRP) outboard, 235 HP, 1978-85

Replaces (OEM)

• 18-3543

Frequently Asked Questions

What does the EMP 75-00403 thermostat replace? The EMP 75-00403 is a direct cross-reference for OEM part number 18-3543, so it installs as a like-for-like replacement without needing to modify the cooling system.

What engines does this thermostat fit? This thermostat fits Johnson/Evinrude (OMC/BRP) outboard engines, specifically 200 HP models from 1977-83 and 235 HP models from 1978-85.

What material is the 75-00403 thermostat made from? It is made from stainless steel, chosen for its resistance to corrosion and mineral scale buildup in raw-water cooling systems.

How much does the EMP 75-00403 thermostat weigh? The thermostat weighs 0.061 pounds.

Is this an OEM or aftermarket thermostat? The EMP 75-00403 is an aftermarket thermostat manufactured to match the specifications and function of OEM part 18-3543.

What are signs my outboard thermostat needs to be replaced? Common symptoms include the engine overheating, an erratic or fluctuating temperature gauge, or the engine running noticeably cooler than normal, all of which point to a stuck or failed thermostat like the one the 75-00403 replaces.

Does the 75-00403 include a gasket? The dossier for the EMP 75-00403 does not list a gasket as part of this item, so buyers should check their existing gasket condition separately.

Can I use the 75-00403 thermostat on a different HP outboard than listed? Fitment for the EMP 75-00403 is confirmed for Johnson/Evinrude 200 HP (1977-83) and 235 HP (1978-85) outboards; applications outside those are not confirmed by the available specifications.

What is the UPC for the EMP 75-00403 thermostat? The UPC for this thermostat is 840080461175.

Why does thermostat material matter on a marine engine? Stainless steel construction, as used in the EMP 75-00403, resists the corrosion that raw-water cooling systems cause in lower-grade metals, helping the thermostat hold its calibrated opening temperature longer.