Sierra 18-8012EP-2 Mercury Fuel Line Assembly 8ft

If you've ever chased down a hard hot restart or caught a whiff of gas in the bilge, you already know the fuel line is one of those parts you don't think about until it fails. This is the Sierra 18-8012EP-2, an 8-foot EPA fuel line assembly built for Mercury outboard engines. It comes ready to run, with the primer bulb, the hose barb, and both end fittings already fitted, so you're not sourcing parts from three different bins to get your boat back on the water.

The hose itself is a rubber core wrapped in polyester braid, then jacketed in a weather-resistant CPE cover. Inside that stack sits a flexible THV barrier layer. That barrier is the part that matters most these days. Modern pump gas carries ethanol, and ethanol is hard on old-style fuel line, drying it out and letting fuel vapor permeate right through the wall. The THV layer is what keeps this hose EPA compliant and keeps the fumes where they belong, inside the line. If your boat still runs the original line from a decade ago, you can usually smell the difference the first time you open the hatch after a hot day.

Fitment is straightforward. The engine end is a 1/8 inch NPT connection sized for Mercury outboards, and the tank end is a 1/4 inch NPT fitting for your portable or built-in tank pickup. The 8-foot length is the sweet spot for most 18 to 22 foot center consoles, giving you enough slack to route cleanly behind the console and around the transom without leaving a big loop to chafe. On smaller tiller boats you'll have some extra to trim and manage, and on bigger rigs with long runs you'll want to plan the routing so you're not fighting vapor lock on a hot restart.

A few install notes from folks who rig these regularly. The polyester braid gives the hose good strength, but it can kink if you force a tight bend behind a console, so pre-form your bends and let the hose settle before you clamp everything down. The 1/8 inch NPT engine fitting is the spot that most often weeps if you rush it, so use a marine-grade thread sealant and snug it to roughly 5 to 7 ft-lb rather than gorilla-torquing it. Where the line passes a transom cutout or a sharp aluminum edge, add a grommet or a bit of chafe guard. The CPE cover shrugs off a lot, but a raw edge under vibration will win eventually.

The EPA primer bulb is the squeeze bulb you'll use to prime the fuel system before that first start of the day. It's built to the same emissions standard as the rest of the assembly. One honest note: any EPA-style bulb adds a little more restriction than the old open-flow bulbs, which is a non-issue on the vast majority of outboards. It's simply the trade-off that comes with a sealed, low-permeation fuel system, and it's what keeps the whole assembly street legal and dock legal.

One more thing worth doing, keep the assembly out of constant direct sun when you can. Like any rubber fuel component, the bulb and cover last longest when they're not baking under UV all season, so a console cover or a bit of shade over the rigging area pays off in the long run.

Who's this for? Anyone running a Mercury outboard who's replacing a tired, cracked, or non-compliant fuel line, or rigging a new-to-you boat and wanting to start with fresh fuel plumbing. It's also the right call after a line has failed an inspection, since this one meets the current EPA low-permeation requirement out of the box. Sierra builds their parts to meet or exceed the original equipment they replace, and they supply a lot of the OEM engine and boat builders directly, so you're getting a part cut to the same standard as what came on the boat.

What it's not: it's not a universal quick-connect kit for every motor, and it's not a fix for a fuel problem that lives somewhere else, like a clogged tank pickup or a failing fuel pump. If you're chasing a fuel delivery issue, replace the line as part of a full look at the system, not as a guess. But if the line is the problem, or it's simply old and you want peace of mind, this is a clean, complete, compliant replacement that goes on with hand tools in an afternoon.