Mercury – Quicksilver Diaphragm Assembly | For 110–300HP DFI OptiMax Outboards | 804533

Overview

Your fuel system’s performance depends on precision parts, and the Mercury Marine 804533 Diaphragm Assembly keeps your OptiMax outboard delivering smooth, consistent power. Built for Mercury 110–300HP DFI OptiMax 2-Stroke engines, this OEM diaphragm is designed for use within the fuel rail, maintaining proper fuel pressure and flow. It’s a small but vital part that helps your engine start cleanly, run efficiently, and perform reliably — even after long days on the water.

Key Features

• Purpose: Maintains correct fuel pressure and flow inside the fuel rail for smooth engine operation.
• Design: Precision-engineered to Mercury’s factory standards for balance and durability.
• Construction: Made from marine-tested materials that resist fuel degradation and ethanol wear.
• Performance: Ensures stable combustion, smooth acceleration, and reduced fuel waste.
• Ease of Use: OEM part for direct replacement — no modifications or tuning needed.

Engine & Boat Compatibility

• Mercury 110–300HP DFI OptiMax 2-Stroke outboards

Performance & Real-World Benefits

The 804533 diaphragm assembly plays a key role in how your OptiMax delivers power. Over time, diaphragms can stiffen or crack due to constant pressure changes and exposure to fuel. Replacing it restores steady fuel flow and helps prevent issues like hard starts, poor throttle response, or inconsistent power.

It’s a simple part that makes a big difference in overall reliability. By maintaining the right balance of pressure within the fuel rail, this OEM diaphragm keeps your engine running strong, efficient, and dependable on every trip.

Why Choose Mercury OEM

The Mercury 804533 is a genuine factory part, built to handle the specific pressures and heat cycles of the DFI OptiMax fuel system. Aftermarket replacements might look similar, but they often can’t match Mercury’s precision or resistance to modern fuel blends.

Mercury’s OEM diaphragms are lab- and field-tested under marine conditions to ensure consistent fuel delivery and long service life. When it comes to the heart of your fuel system, using OEM ensures you’re running with the same reliability your engine was built for.

FAQ

Q1: What does this part do?
It regulates fuel pressure within the fuel rail, ensuring the injectors receive consistent flow.

Q2: What engines does it fit?
It fits Mercury 110–300HP DFI OptiMax 2-Stroke outboards.

Q3: Why replace the diaphragm?
Over time, it can harden or crack, causing fuel delivery issues and inconsistent engine performance.

Q4: Is this a direct replacement?
Yes — it’s an OEM part designed for perfect fit and function with no modification.

Q5: Why choose OEM?
Mercury’s OEM diaphragms are precision-engineered and ethanol-safe, giving you long-term durability and consistent performance.