# 864493 Mercury MerCruiser MerCruiser Closed Cooling Thermostat | Genuine Quicksilver OEM Part

🔧 Product Description

  

Genuine Quicksilver Closed Cooling Thermostat - Part Number: 864493

  

A genuine Quicksilver 170°F thermostat for MerCruiser closed cooling systems. This thermostat is used on selected MCM 4.3L, 5.0L, 5.7L and 6.2L MPI engines with dry-joint exhaust and closed cooling, helping regulate coolant temperature inside the closed cooling circuit.

  

⚙️ Key Features

  

• Genuine Quicksilver OEM closed cooling thermostat

• Correct Mercury part number 864493

• 170°F / 77°C thermostat

• Used on selected MerCruiser MPI engines with closed cooling

• Designed for dry-joint exhaust cooling-system configurations

  

🔄 Supersession & Cross Reference

  

OEM Supersession Chain:

  

• 864493 current OEM thermostat reference

  

OEM / Related Numbers:

  

• 864493

• 25-8071341 related thermostat seal

• Closed Cooling Thermostat 170°F

  

Aftermarket / Verified Equivalents:

  

• Mallory: 9-43015

• Recmar: REC864493

  

🚤 Compatibility

  

Commonly used on:

  

• MerCruiser closed cooling systems with dry-joint exhaust

  

Typically suits:

  

• Engine models:

• MerCruiser MCM 4.3L MPI engines with dry-joint exhaust and closed cooling

• MerCruiser MCM 5.0L MPI engines with dry-joint exhaust and closed cooling

• MerCruiser MCM 5.7L MPI engines with dry-joint exhaust and closed cooling

• MerCruiser MCM 350 MAG MPI engines with dry-joint exhaust and closed cooling where specified

• MerCruiser MCM 6.2L MPI engines with dry-joint exhaust and closed cooling

• MerCruiser V6 / V8 MPI closed cooling thermostat applications requiring 864493

  

• Engine Type: MerCruiser petrol V6 / V8 MPI

• Temperature Rating: 170°F / 77°C

• System Type: Closed cooling thermostat

  

🔌 Function

  

The thermostat regulates coolant flow through the closed cooling system so the engine maintains the correct operating temperature.

  

Common signs of failure:

  

• Engine overheating

• Engine running below normal temperature

• Slow warm-up

• Coolant temperature fluctuation

• Thermostat stuck open, stuck closed or corroded

  

📦 Condition

  

• Genuine Quicksilver part

• Brand new

• Supplied in original or equivalent packaging

## Details

- **Price:** 54.9 AUD
- **Vendor:** Quicksilver
- **Tags:** Quicksilver Marine Parts | Oils Service Kits & Engine Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 54.90 AUD | In stock |

## Images

- 864493 Mercury MerCruiser MerCruiser Closed Cooling Thermostat | Genuine Quicksilver OEM Part

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> Source: [Sawley's Auto and Marine](www.sawleysautoandmarine.com.au/products/864493-mercury-mercruiser-mercruiser-closed-cooling-thermostat-genuine-quicksilver-oem-part)
> Updated: 2026-05-17