# 804533 Mercury MerCruiser Diaphragm Assembly | Genuine Quicksilver OEM Part

🔧 Product Description

  

Genuine Quicksilver Diaphragm Assembly - Part Number: 804533

  

Genuine Quicksilver/Mercury diaphragm assembly for Mercury OptiMax DFI two-stroke outboard fuel rail applications. This OEM diaphragm is used in compatible fuel rail assemblies and helps maintain correct fuel and air pressure regulation for reliable direct fuel injection performance.

  

⚙️ Key Features

  

• Genuine Quicksilver/Mercury OEM diaphragm assembly

• Designed for Mercury OptiMax DFI two-stroke outboards

• Used in compatible fuel rail / tracker diaphragm applications

• Helps maintain correct fuel rail pressure control

• Critical fuel-system service component for DFI engine performance

  

🔄 Supersession & Cross Reference

  

OEM Supersession Chain:

  

• 804533

  

OEM / Related Numbers:

  

• 804533

• 804533 diaphragm assembly

• Tracker diaphragm fuel rail reference

• Starboard fuel rail diaphragm application

• 804533T related service reference where listed

  

Aftermarket / Verified Equivalents:

  

• Aftermarket tracker diaphragm equivalents available for matched OptiMax fuel rail applications

• REC: related OptiMax diaphragm replacement references where matched by application

  

🚤 Compatibility

  

Commonly used on:

  

• Mercury OptiMax DFI two-stroke outboard fuel rail assemblies

• Mercury 2.5L and 3.0L OptiMax fuel pressure control systems

  

Typically suits:

  

• Engine models:

• Mercury 110HP OptiMax DFI two-stroke outboards

• Mercury 115HP OptiMax DFI two-stroke outboards

• Mercury 135HP OptiMax 2.5L DFI two-stroke outboards

• Mercury 150HP OptiMax 2.5L DFI two-stroke outboards

• Mercury 175HP OptiMax 2.5L DFI two-stroke outboards

• Mercury 200HP OptiMax 3.0L DFI two-stroke outboards

• Mercury 225HP OptiMax 3.0L DFI two-stroke outboards

• Mercury 250HP OptiMax 3.0L DFI two-stroke outboards

• Mercury 300HP OptiMax 3.0L DFI two-stroke outboards

• Mercury 330HP OptiMax DFI two-stroke outboard applications where 804533 diaphragm is specified

• Starboard fuel rail tracker diaphragm applications on Mercury 2.5L 135HP-175HP OptiMax engines

• Starboard fuel rail tracker diaphragm applications on Mercury 3.0L 200HP-300HP OptiMax engines

  

• HP Range: 110HP - 330HP

• Engine Type: Mercury OptiMax DFI two-stroke outboard fuel rail / pressure control system

• Year Range: Application dependent by OptiMax model, fuel rail design and serial number

  

🔌 Function

  

The diaphragm assembly helps regulate pressure inside the OptiMax fuel rail system. Correct diaphragm operation is essential for stable fuel delivery, air/fuel pressure balance, idle quality and direct-injection performance.

  

Common signs of failure:

  

• Hard starting

• Rough idle or misfire

• Poor acceleration

• Fuel pressure instability

• Engine running rich or lean

• Fuel smell or leakage around fuel rail

• Diagnostic faults related to fuel or air pressure regulation

  

📦 Condition

  

• Genuine Quicksilver part

• Brand new

• Supplied in original or equivalent packaging

## Details

- **Price:** 136.0 AUD
- **Vendor:** Quicksilver
- **Tags:** Quicksilver Marine Parts | Oils Service Kits & Engine Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 136.00 AUD | In stock |

## Images

- 804533 Mercury MerCruiser Diaphragm Assembly | Genuine Quicksilver OEM Part

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> Source: [Sawley's Auto and Marine](www.sawleysautoandmarine.com.au/products/804533-mercury-mercruiser-diaphragm-assembly-genuine-quicksilver-oem-part)
> Updated: 2026-05-30