Number 40: Spill? What spill? Products that keep fuel where it belongs—in your tank

Boat/US Magazine, March, 2005 by Joni Sralla Turken

You're at the fuel dock, pumping fuel as fast as you can, when your grandson tugs on your arm, begging for an ice cream sandwich. Momentarily distracted by your search for change, and before you can say "Eskimo Pie," fuel is tumbling out of your tank vent and down the side of the hull. While a sheen starts to spread, you try to play it cool. It's just a couple of drops, right?

Fuel tanks on boats are not pressurized like they are in automobiles, so inboard boat tanks have an air vent to relieve the pressure that builds during fueling. Unfortunately, when your tanks are filled quickly or overfilled, these vents are notorious for burping fuel out into the water.

Are you worried about the effects of careless fueling on the environment? Do you have an aversion to retouching your gel coat, or for writing checks for pollution fines like the ones you could get under federal law for causing a fuel sheen on the water?

If so, the BoatU.S. Foundation has tested 10 products that promise fewer fueling spills, or could help you avoid overfilling.

The Hardware

Using products obtained from manufacturers, we tried out four "inline fuel-air separators" from Attwood and Racor, ranging in price from about $20 up to $110. Next we tested three varieties of deck fill-vent combinations, also called "vented fills," from Attwood and Perko, which retail from $20 to $60. Last in this category, we tested a unique device called the Seacurefill Fuel Recovery System which retails for about $139.

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In separate tests, we obtained electronic fuel management systems (also called fuel computers or flow meters) and installed them on boats borrowed for this test. We tried the FloScan Series K9000 with GPS interface, which runs for about $1,400 per engine, and the Navman TrackFish 6600, a unit which includes a chart plotter, fish finder, and fuel computer in one. This loaded unit retails for about $1,900. Without all the fancy features, however, a basic fuel flow meter can cost as little as $200.

To test the hardware, we built a mockup of a boat fuel tank system, complete with a tank vent. On the "deck" of our model, we installed the vented deck fills. Below deck, accessible hoses allowed staff members to install the inline devices. For inline device testing we used a regular deck fill like you might find factory-installed. One product was tested at a time; there were no combinations of products, such as a deck fill and inline separator.

Due to obvious hazards, we did not use real gas or diesel for our testing, but instead used carefully-formulated solutions of soapy water to mimic the foaming quality and viscosity of both gas and diesel. To pump our "fuels," we used two actual fuel nozzles--one standard (3/4") and one large (1-1/4")--which we attached to an electric water pump and pumped at both 10 gallons per minute and 20 gallons per minute. During testing, we pumped at full force every time until the nozzle automatically cut off. We did not top off.

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To test the fuel management systems, we installed the Navman TrackFish 6600 on a 21-foot Stratos center console, powered with a single 200-hp gas outboard. We then took the boat on trial runs on Chesapeake Bay, varying the throttle, trim, and tilt settings to monitor fuel usage. We also had two FloScan Series K9000 professionally-installed on a 55-foot Fleming power cruiser with twin Caterpillar engines and monitored its readouts during a 1,500 mile snowbird voyage down the Intercoastal Waterway.

All Wet

After 24 different tests on the mockup, on both inline fuel-air separators and vented deck fills, we noticed a definite trend. In test after test, overflow bubbled out of the deck fill when the tank became full, often before the nozzle's auto shut-off even had a chance to engage. In other words, the pressure created by pumping fuel at a high rate of speed caused fuel to escape if not from the vent, then from somewhere, and in many cases, that somewhere was on deck.

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There was one positive exception. The Racor Lifeguard Fuel/Air Separator for gas/diesel (Model LG-100), an inline separator shaped like a small football, worked perfectly during every test, with no fuel escaping from either the vent or the deck fill. We believe it worked so well because of its large size, which allowed plenty of room for foamy fuel to bubble up, functioning like an expansion reservoir, without cutting off the air vent too quickly and causing backsplash from the fill. To confirm our findings about the inline fuel-air separators, we installed each of them individually on a colleague's Tiara Pursuit 24-foot center console so we could try them with actual fuel. In these tests, the Racor Model LG-100 was again the only unit that did not permit a single drop of fuel to escape when fueling rapidly.

Another exception was the Seacurefill Fuel Recovery System. It did the job, but requires an extra hole being cut in your boat, plus cumbersome additional steps during fueling.

Knowledge is Power