# 8M0228411 Mercury MerCruiser Thermostat | Genuine Quicksilver OEM Part

## 🔧 Product Description

**Genuine Quicksilver Small-Outboard Thermostat - Part Number: 8M0228411**

A genuine Quicksilver thermostat for selected Mercury and Mariner 6HP to 18HP two-cylinder outboards.

The thermostat controls cooling-water flow through the cylinder block, allowing the engine to warm correctly before opening to maintain its designed operating temperature.

## ⚙️ Key Features

-   Genuine Quicksilver OEM thermostat
-   Correct current Mercury part number 8M0228411
-   Supersedes earlier thermostat 803665
-   Used on selected two-cylinder international outboards
-   Recmar and Tohatsu replacement references available

## 🚤 Compatibility

### Commonly used on

-   Mercury and Mariner two-cylinder international outboard cooling systems
-   Corresponding Tohatsu-manufactured thermostat applications

### Typically suits

-   Engine models:
-   Mercury / Mariner 6HP 2-cylinder - serial 0N027903 to 0N055109
-   Mercury / Mariner 6HP 2-cylinder - serial 0N055110 and above
-   Mercury / Mariner 8HP 2-cylinder - serial 0N027903 to 0N055109
-   Mercury / Mariner 8HP 2-cylinder - serial 0N055110 and above
-   Mercury 8HP SeaPro - serial 0N014717 to 0N055109
-   Mercury 8HP SeaPro - serial 0N055110 and above
-   Mercury / Mariner 9.8HP 2-cylinder - serial 0N007788 to 0N055109
-   Mercury 9.8HP SeaPro - serial 0N055110 and above
-   Mercury / Mariner 9.9HP 2-cylinder - serial 0N059858 and above
-   Mercury / Mariner 9.9HP 2-cylinder - serial 0N260037 and above
-   Mercury / Mariner 15HP 2-cylinder - serial 0N001590 to 0N055284
-   Mercury / Mariner 15HP 2-cylinder - serial 0N055285 and above
-   Mercury / Mariner 18HP 2-cylinder - serial 0N001590 to 0N055284
-   Mercury / Mariner 18HP 2-cylinder - serial 0N055285 and above
-   HP Range: 6HP - 18HP
-   Engine Type: Mercury / Mariner two-cylinder carburetted outboard
-   Year Range: Serial-number controlled international production

## 🔌 Function

The thermostat restricts cooling flow during warm-up and opens at its calibrated temperature to maintain stable engine temperature.

## ⚠️ Common Signs of Failure

-   Engine overheats because the thermostat remains closed
-   Engine runs too cold because the thermostat remains open
-   Poor idle during warm-up
-   Heavy corrosion or salt deposits
-   Irregular cylinder-block temperature

## 🔄 Supersession & Cross Reference

### OEM Supersession Chain

-   8M0228411 → Supersedes 803665
-   803665 earlier OEM thermostat reference

### OEM / Related Numbers

-   8M0228411
-   803665
-   853704
-   804540
-   Tohatsu: 350-01030-0
-   Tohatsu: 350-01030-1
-   Tohatsu: 350-01030-2

### Aftermarket / Verified Equivalents

-   Recmar: REC804540
-   Tohatsu / Nissan Marine: 350-01030-2
-   Sierra: 18-3638

## 📦 Condition

-   Genuine Quicksilver part
-   Brand new
-   Supplied in original or equivalent packaging

## Details

- **Price:** 94.45 AUD
- **Vendor:** Quicksilver
- **Type:** Cooling System
- **Tags:** Quicksilver Marine Parts | Oils, Service Kits & Engine Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 94.45 AUD | In stock |

## Images

- 8M0228411 Mercury MerCruiser Thermostat | Genuine Quicksilver OEM Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/8m0228411-mercury-mercruiser-thermostat-genuine-quicksilver-oem-part)
> Updated: 2026-09-06