Sierra 18-8868-2 Electric Fuel Pump for MerCruiser 4.3L/5.0L/5.7L

If your MerCruiser gas engine is starving for fuel, cranking but not catching, or you've pulled the cover after winter layup and found a cracked pump body, this is the electric fuel pump that gets you back on the water. Sierra built the 18-8868-2 to drop into 4.3L V6, 5.0L V8, and 5.7L V8 MerCruiser gasoline engines, and it comes with the fittings and O-rings you need to seal it up right the first time.

This is a full electric fuel pump assembly, not just a diaphragm kit. The dual threaded ends let you thread your existing fuel lines straight onto the pump, and because the fittings and O-rings ship in the box, you're not making a second trip to the parts counter halfway through the job. Sierra engineers their parts to meet or exceed the original equipment they replace, so the flow and pressure line up with what your engine's fuel system was designed around.

Who needs one? Any boater running a carbureted or fuel-injected MerCruiser small block or V6 that's showing fuel delivery trouble. Hard starts, stumbling under load, a whining pump, or a slow pressure bleed-down after shutdown are all classic signs. If you've traced the problem past the filter and the lines and landed on the pump, this is the part that fixes it. It's also a smart spare to carry if you cruise well offshore and don't want a fuel pump failure to end your season.

A few things we've learned installing these. Relieve the fuel system pressure and disconnect the battery before you touch anything, and keep a fistful of shop rags handy because a little gas is going to spill no matter how careful you are. When you fit the new O-rings, lubricate them with clean gasoline instead of grease. Grease can contaminate the fuel and swell the wrong seals. Snug the threaded fittings firmly but don't gorilla them down, since overtightening is the fastest way to crack a fitting or distort an O-ring. Take a minute to double-check that both threaded ends are square before you tighten, because a cross-threaded fitting will weep fuel no matter how hard you crank on it.

Routing matters more than people think in a hot engine bay. Keep the fuel line clear of the exhaust manifold so radiant heat doesn't cook the hose and harden the seals over a couple of seasons. On the EFI 5.0L and 5.7L V8s, leave a little slack in the line so normal engine movement doesn't tug the connection loose at the pump. And if you don't already run a spin-on fuel and water separator upstream, add one. A clean 10-micron filter ahead of the pump keeps grit off the new O-rings and helps the whole assembly last.

One honest note on modern pump gas. The ethanol in most dock fuel is harder on rubber than the straight gasoline these engines were born with. That's not a knock on this pump, it's just the reality of the fuel you're buying. Pull the cowling once a season, eyeball the O-rings and the barb ends for weeping or cracking, and you'll catch a problem in the driveway instead of three miles out. This pump is gasoline-rated and handles the E10 fuel you'll find at nearly every marina.

Bottom line, the Sierra 18-8868-2 is a straightforward, engine-specific replacement for a part that strands a lot of boats every summer. It fits the most common MerCruiser gas engines, it arrives with the hardware to finish the job, and it carries Sierra's reputation for marine parts that survive the heat, vibration, and moisture of life in the bilge. Confirm it against your original pump, order it, and get your weekend back.