Mercury - Fuel Line Assembly, 9 Ft., 5/16" I.D. Fuel System 32-8M0053989. Overview. If your outboard's been a little stubborn-taking forever to prime, coughing when you bump the throttle, or losing steam when the water gets choppy-a tired fuel line is often the culprit. This 9-foot Mercury fuel line is basically a fresh start. It's a straight 5/16" hose with no connectors attached, so you can rig it exactly how your tank and engine are set up. The hose has the right feel to it-flexible enough to