Mercury – Fuel Line Coupler | Composite Construction | 8M0001721

Overview

There are a lot of small parts on a boat that you never think about until the day they fail. A fuel line coupler is one of them. When it’s doing its job, you do not notice it at all — and honestly, that is exactly how it should be. Whether you are drifting over a calm flat at sunrise or pushing through a choppy inlet on the ride home, you want every connection in your fuel system to feel steady and secure. Mercury Marine part 8M0001721 gives you that quiet confidence. It is a simple, reliable coupler designed to do one thing well: keep your fuel moving without interruption so you can focus on where the water takes you next.

Key Features

• Composite plastic fuel line coupler designed for smooth, consistent flow
• Connects a .375 inch inside diameter fuel line to a .3125 inch inside diameter fuel line
• Produced to Mercury Marine original equipment specifications
• Durable construction engineered for marine fuel systems
• Ideal for replacing worn or aging connectors during routine maintenance

Engine & Boat Compatibility

• Works with select Mercury and Mariner outboards requiring a .375 in. to .3125 in. fuel line connection
• Compatible with many portable tank setups
• Suitable for bass boats, aluminum fishing boats, pontoons, small center consoles, and inflatable tenders
• Appropriate for both older and newer fuel systems when downsizing or adapting line sizes

Performance & Practical Benefits

A fuel line coupler may be small, but its job is not. This connector sits right in the path of your engine’s lifeline, and when conditions get rough or your motor is working hard, you want a connection that stays tight. Mercury’s composite design feels solid and holds its grip without slipping or deforming in heat. You will notice how clean the connection feels when you seat the lines — no wobble, no soft spots, just a snug fit that inspires trust.

In real use, this coupler keeps fuel delivery steady, even when your boat is taking wakes or bouncing through afternoon chop. It also installs easily, which any weekend mechanic will appreciate. Many boaters use it when modernizing older fuel systems or when repairing sections where the line sizes differ. It is the kind of part you replace once, then forget about because it simply works.

Why Buy OEM

A genuine Mercury Marine part is more than a convenient match — it is a guarantee. With OEM parts, you know the material quality has been tested against heat, fuel exposure, vibration, and long hours on the water. Aftermarket connectors may look similar, but the tolerances are rarely as precise, and in a fuel system, precision is everything. When you use a Mercury Marine coupler, you know it was built for your engine, built for the marine environment, and built to last. It is a small investment that protects a much larger one.

FAQ

Q1: Which Mercury engines does this fuel line coupler fit?

It is used in systems needing a connection between .375 inch ID fuel line and .3125 inch ID fuel line, common across many Mercury and Mariner outboards.

Q2: What makes this different from aftermarket couplers?

OEM fit, tighter tolerances, and materials that hold up better against vibration, fuel exposure, and heat.

Q3: How do I know if this is the right replacement?

Check your fuel line diameters or your manual. If your system transitions between these two sizes, this is the correct part.

Q4: Can this be used in saltwater and freshwater?

Yes, the composite construction performs well in both environments.

Q5: Is installation straightforward?

Yes, most owners can install it with simple hand tools during routine fuel line service.