# 0435491 Evinrude Johnson Thermostat AY | Genuine OEM BRP Outboard Part

🔧 Product Description

  

Genuine BRP Evinrude Johnson 143°F Thermostat Assembly - Part Number: 0435491

  

A genuine BRP cooling-system thermostat for selected 90HP, 115HP, 150HP and 175HP Evinrude and Johnson two-stroke outboards.

  

The thermostat begins opening at approximately 143°F or 62°C, regulating cooling-water circulation through the cylinder block and cylinder heads. Correct temperature control helps the engine warm up evenly while preventing excessive operating temperature under load.

  

⚙️ Key Features

  

• Genuine BRP Evinrude Johnson OEM thermostat

• Correct OEM part number 0435491

• Common unprefixed number 435491

• Approximately 143°F / 62°C opening temperature

• Used on selected 60-degree V4 and V6 engines

• Wax-pellet thermostat construction

• Sierra and Mallory replacements available

  

🔄 Supersession & Cross Reference

  

OEM / Related Numbers:

  

• 0435491

• 435491

• Mercury / Quicksilver: 8M6010305

• OEM Description: Thermostat Assembly

• Temperature Rating: Approximately 143°F / 62°C

• Thermostat diaphragm and pressure-control components vary by engine model

  

Aftermarket / Verified Equivalents:

  

• Sierra: 18-3544

• Mallory: 9-43032

• Aftermarket 143°F thermostat replacing 0435491

• Generic replacement cross-referenced to 435491 and 8M6010305

  

🚤 Compatibility

  

Typically suits selected:

  

• 90HP: approximately 1995-2006

• 115HP: approximately 1995-2006

• 150HP: approximately 1993-2006

• 175HP: approximately 1993-2006

• 60-degree V4 and V6 two-stroke engine families

• Carburetted, FICHT and applicable direct-injection engines whose diagrams specify 0435491

  

Important fitment note:

  

• Some engines require one thermostat per cylinder bank.

• Confirm the quantity required by the cylinder-and-crankcase diagram.

• Do not substitute thermostat 0436195 solely because it has a similar temperature rating.

• Grommets, seals, covers, springs and diaphragms are separate unless specifically included.

  

🔌 Function

  

The thermostat restricts water flow during warm-up and opens progressively as the engine reaches operating temperature.

  

Common signs of thermostat failure:

  

• Engine overheats at idle or under load

• One cylinder bank runs hotter than the other

• Engine remains excessively cold

• Over-temperature warning activates

• Salt deposits prevent the thermostat from moving

• Thermostat remains open when cold

• Thermostat does not open in heated water

• Rubber seal or thermostat frame is damaged

  

Installation considerations:

  

• Replace thermostats in matched pairs where the engine uses two

• Inspect thermostat covers and sealing surfaces

• Replace damaged grommets and seals

• Remove salt deposits from the thermostat cavity

• Do not scratch aluminium sealing surfaces

• Confirm the replacement begins opening near 143°F / 62°C

• Check cooling-water flow after installation

• Verify both cylinder-bank temperatures during operation

  

📦 Condition

  

• Genuine BRP Evinrude Johnson OEM part

• Brand new

• Supplied in genuine or equivalent protective packaging

## Details

- **Price:** 60.13 AUD
- **Vendor:** BRP (Evinrude/Johnson)
- **Tags:** Evinrude Johnson Outboard Parts | BRP Marine Engine Parts & Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 60.13 AUD | In stock |

## Images

- 0435491 Evinrude Johnson Thermostat AY | Genuine OEM BRP Outboard Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/0435491-thermostat-ay)
> Updated: 2026-07-12