Mercury – Check Valve Assembly | Fuel System Component | Marine-Grade Construction | 424811

Overview

Fuel flow needs to move one way and one way only — that’s where the Mercury Marine 424811 Check Valve Assembly comes in. Built for Mercury 150–300HP EFI TwoStroke outboards, this small but essential part keeps your system pressurized and prevents fuel from flowing backward. It’s designed and calibrated by Mercury to hold the exact blowoff pressure your EFI engine needs to run right. Made from marine-tested materials that stand up to heat, vibration, and ethanol-blended fuels, it helps your engine start clean, idle smooth, and stay dependable trip after trip.

Key Features

• Purpose: Stops fuel from flowing backward, keeping the system pressurized and stable.
• Material: Constructed from corrosion-resistant, fuel-safe materials designed for marine use.
• Performance: Maintains the factory blowoff pressure your EFI system requires for consistent operation.
• Design: Engineered to Mercury OEM standards for fit, flow, and long-term reliability.
• Durability: Handles constant vibration, fuel pressure, and high temperatures without leaking or sticking.
• Compatibility: Fits Mercury 150–300HP EFI TwoStroke outboards.

Engine & Boat Compatibility

• Mercury 150HP, 175HP, 200HP, 225HP, 250HP, and 300HP EFI TwoStroke outboards.
• Commonly found on offshore fishing boats, bass boats, and performance setups.
• Safe for both freshwater and saltwater environments.
• Direct replacement for the original check valve assembly — no modifications needed.

Performance & Real-World Benefits

A good check valve keeps your fuel system running at the pressure your engine was built for. The 424811 valve prevents backflow, so your fuel injectors stay primed and ready. That means faster starts, smooth throttle response, and steady fuel delivery even after long runs or storage.

When a valve starts to fail, pressure drops and fuel drains back toward the tank — causing rough starts or uneven performance. Replacing it with this Mercury OEM valve ensures the right pressure balance and reliable fuel flow every time you hit the water.

Why Choose Mercury OEM

The Mercury 424811 isn’t just a part — it’s a pressure-calibrated component made to exact factory standards. Aftermarket valves can look similar, but small differences in internal design or spring tension can throw off your EFI system’s performance.

Mercury’s OEM check valves are tested for consistent blowoff pressure, fuel resistance, and reliability in harsh marine conditions. It’s a small upgrade that guarantees smoother running and fewer fuel system headaches over the long haul.

FAQ

Q1: What engines use this valve?
It fits Mercury 150–300HP EFI TwoStroke outboards.

Q2: What’s its function?
It maintains pressure and prevents fuel from flowing backward in the EFI system.

Q3: Can it handle ethanol-blended fuel?
Yes — it’s designed for modern fuel blends and marine-grade durability.

Q4: What happens if the valve fails?
You may notice hard starting, uneven idle, or fuel draining back toward the tank.

Q5: Why OEM instead of aftermarket?
OEM valves match your engine’s exact pressure calibration and are built to survive the marine environment.