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Installing a Diesel Priming System on Your Boat

Story and photography by Capt. Vincent Daniello

Once you’ve got a unit installed, here’s how it works. With the pump running, crack the bleed screw in the top of the Separ fuel
filter as shown until air-free fuel flows. Dahl filter housings are similar. Racor filters don’t have a bleed screw, so leave the top of the filter cracked and bump the switch until fuel seeps out.

Photography by Capt. Vincent Daniello

Purists may point out that these brands of primary fuel filters work best under suction—not under pressure. This is true for large-volume fuel-transfer or polishing systems, but the small bit of fuel pushed through while priming gets cleaned just fine. Still, if you opt to install it downstream of the primary filter instead of upstream, Reverso’s system works well drawing fuel and air through the primary as long as return fuel flow is adequate. Simply seal the filter top and/or bleed screw and run the pump. You’ll see fuel mixed with air, and eventually clean fuel, moving through the clear filter bowl.

Once the primary filter is primed, “The pump pushes fuel and air all the way through the system and back to the tank,” says Carlos Frias, senior mechanic at New England Boatworks in Portsmouth, Rhode Island ( “If the engine has a hand pump, give it a few strokes. If you feel resistance you know it’s primed.” But there is one caveat, Frias says: Most diesels incorporate a pressure valve just before fuel returns to the tank. If the pump doesn’t build the requisite pressure, the engine won’t prime itself. Reverso’s system comes preset at either 15 or 22 psi. Check with your mechanic or Reverso to get the right pump, and order either left-to-right fuel flow or vice-versa, to facilitate mounting within your specific fuel line route.