Products to Keep Fuel Where it Belongs—In Your Tank
It’s hot, the harbor is crowded, and you have been circling the fuel dock for 25 minutes waiting your turn. Finally you snag a spot on the dock. You’re pumping diesel as quick as you can when your grandson tugs on your arm, begging for spare change for an ice cream sandwich from the ships store.
With your wallet hand deeply in the pocket of your Bermuda shorts, your tanks are suddenly and unpredictably full. Before you can say “Eskimo Pie,” pink diesel is tumbling out of your tank vent, down the side of your new gel-coated hull, and hitting the water—naturally, right as a mama duck leads a family of fuzzy ducklings by. In one careless moment, you’ve streaked your gelcoat, broken a federal environmental law, and insulted nature right in her face.
Has this ever happened to you or someone you know? You aren’t the only one.
Fuel tanks on boats are not pressurized like they are in automobiles. Because of this, inboard boat tanks have an air vent to relieve the pressure that builds while filling a tank. As a result, no matter what kind of boat you have and no matter how careful you are during fueling, it is really quite easy to spill fuel out into the water if you don’t take a few simple precautions.
with the law. Under federal law, you are required to report a fuel
or oil spill, no matter how small, if it is enough to cause
What’s a Boater to Do? No matter what size boat you have, there is something you can do to prevent accidental fuel spills. If you’ve got a big boat with big tanks, it might be one approach, while if you have a sailboat with a small tank, another. We tested a variety of devices—from hardware you install, to computers thatcan make you smarter about your fuel usage—and were thrilled to see so many options to keep drips and drops out of the water.
Plus, in the
course of testing, we got familiar with different absorbent pads, catchment
devices, fueling bibs and donuts, as well as
In this consumer product testing, conducted in October 2004, we evaluated readily available boat products including inline fuel/air separators, combination deck fill and vents, and fuel computers. With strict orders not to spill one single drop of fuel into the environment, we came up with two different methods of testing these products: first, a landside boat mock-up using a soapy water recipe as our fuel product and second, several friends’ boats, which allowed us to test the inline fuel/air separators and fuel computers on real vessels. Here’s how we did it.
After our initial control tests, we substituted the black 5/8” USCG approved vent line with clear vinyl tubing in order to see the bubbly “fuel” venting as it occurred. (Please note that clear tubing is not approved by the Coast Guard for fuel.) Then, to put these products to the real test, we installed each inline fuel/air separator and each fuel computer on motor boats ranging in size from 21’ to 55’. Since the deck-mounted combination deck fill and vent units would have required drilling holes in our friends’ boats (and friends with boats are good friends to keep), those products were only tested on our mock-up.
Using soapy water solutions, we formulated realistic substitutes for both
gasoline and diesel. After evaluating a variety of soap products, we decided
on using car wash soap, which bubbled up initially then settled down rapidly,
just like fuel. After many test trials, we settled on adding ¼ teaspoon
of car wash soap to 15
The Method: Some of the products tested were designed for gas, some for diesel and some for either. We only tested products with their intended fuel. To deliver the fuel, we stuck to the same method in test after test. We filled the tank at full speed until the nozzle clicked off. We did not top off. We felt that this method best represented the practices of the majority of boaters, and it allowed us to provide the same fuel delivery speed each time.
An inline fuel/air separator is a simple and inexpensive device that is installed directly into your tank’s overboard vent line. As the fuel tank gets full and frothy fuel surges up from the tank, a ball rises and cuts off the travel of fuel that would normally escape overboard via the vent. Some of these devices claim to help shut off automatic fuel nozzles when your tank is full. Although none of the devices tested had a special whistle integrated to indicate fuel level (a feature we really loved in a now discontinued product) there was still an audible difference in some of the units when the tank was near full.
RACOR FUEL/AIR SEPARATOR for GAS ONLY (Model #LG50; retails for $92.99). The Racor LG50 is the smaller, gasoline-only version of the Racor LG100 and is about the size of a large salt shaker. It functions the same way: a ball rises within the housing, preventing vented fuel from exiting the tank. However, this unit did not work as well as its bigger brother. It could not be disassembled, so we couldn’t tell exactly what was going on, but we surmised that the ball would float up as designed but would block the fuel and air too rapidly. This sudden shut off of fuel and air to theoverboard vent surprised us when it caused backsplash through the deck fill, even when filling at the slower speed of 10 gpm. For the 20 gpm test, the backsplash was even more prominent, which was also true with the other smaller devices in this category. The Racor LG50 can be ordered through BoatU.S. and West Marine stores, internet and catalog sales.
P-TRAP FUEL SURGE PROTECTOR (Model #1689; retails for $21.54).
This unit looks different because it combines a fuel separator, fuel vent
and flame arrestor in one unit and is roughly the size and shape of a fist.
The Attwood P-Trap is installed on the inside of your hull with the vent
portion replacing your existing overboard vent on the outside of your hull.
Since this unit is plastic, we were concerned about the possibility of crushing
it on a piling in a docking maneuver. To test, we again delivered fuel at
10 gpm and 20 gpm and the results
We did not slow down our pumping, even when we heard gurgling, which may account for some of the less than positive results. But since many people lock the pump handle and walk away, we felt that filling at full speed simulated a realistic situation. For these reasons we do not recommend using a hands-free device and we do recommend keeping your hands and face clear from the filler hole.
In general, the larger the unit and the slower you pumped, the better these devices performed. The fact is, there is simply is no substitute for careful and deliberate fueling. Listen to these devices, know how much fuel you need and slow down when you think you are near full. Do not top off and these devices may suit you just fine.
VENTED DECK FILLS
You may also have to cut a slightly larger deck opening to accommodate this larger fixture. This new unit allows for movement of air into and out of the tank via the cap and essentially functions as a vent when not refueling. For this reason, vented deck fills are not air tight, and therefore are NOT watertight.
Both Attwood and Perko specifically bring this trait to your attention and urge you not to install this device in a location that can become substantially flooded or submerged. The Seacurefill device uses your existing vent and functions somewhat differently so water intrusion is not a problem with this unit.
During our mock-up test, with the nozzle fully inserted and pumping at both 10 gpm and 20 gpm, fuel managed to back up the filler pipe and trigger the auto shut-off on the pump nozzle too late. At 10 gpm, the splash guard managed to redirect most of the fuel back into the tank, but at 20 gpm, fuel worked its way past the guard and ended up on our deck. Since the unit was mounted on a 45 degree angle, the vent was actually slightly higher than the fill opening and we wondered if this characteristic contributed to the auto nozzle clicking off too late.
On the plus side, its built-in plastic splash guard minimized “misting,” which occurred on other models when vented fuel bounced off the nozzle, keeping the deck essentially dry until the tank became full. This unit requires a grounding wire to prevent sparking when a nozzle is inserted, so please refer to the instructions for safe installation. The Attwood deck fill and can be ordered through the BoatU.S. and West Marine catalog sales special orders department.
Because of its hinged design, there was no beaded retainer chain for the lid getting in the way of visibility into the neck of the deck fill. When the fuel tank was nearly full, we could easily see that the vent was doing its job by redirecting vented fuel back down the filler neck during the refueling process. As in other tests, we waited for the auto shut-off device to disengage. Unfortunately at both 10 gpm and 20 gpm testing, fuel spilled out of the filler neck suddenly just as the nozzle clicked off and flowed onto the deck. We also found that the larger nozzle (delivering 20 gpm) did not fit very well in the deck opening and we experienced slight misting on the deck during the fueling process as a result of the vented spray hitting the nozzle and landing on the deck.
This unit and other Perko models can be ordered through the BoatU.S. and West Marine catalog sales special orders department.
During testing, we experienced results similar to the other models previously tested. At 10 gpm, the tank would suddenly become full and backsplash would spill out of the deck fill just as the automatic shut-off nozzle disengaged. And at 20 gpm, even more fuel flowed from the deck fill and onto our deck. This unit can be ordered through the BoatU.S. and West Marine catalog sales special orders department.
SEACUREFILL FUEL RECOVERY SYSTEM (1 ½” Model; retails for $139.00). The Securefill is a different kind of vented deck fill. Instead of having an integrated vent, it requires you to permanently install a new vent fitting in the deck adjacent to your existing deck fill. It works by redirecting the vented fuel back into the original deck fill via a piece of clear vinyl tubing that you must attach temporarily each time you fill up your boat. The concept is simple - the clear tubing literally allows you to see the venting process during refueling so you will react and slow down in response to the rising fuel bubbles.
To install, you must cut a hole in your deck about the same size as your existing deck fill. You do not have to abandon your existing vent, but below deck, you will need to fit your existing 5/8” vent tube to a nipple on the bottom of the unit and add another short section from the Seacurefill unit to the existing overboard vent. This allows for the boat’s vent system to breathe and operate normally when not refueling.
We tested this device as we did the other units – at both 10 gpm and 20 gpm and pumped until the handle clicked off. In a way, this was an unfair disadvantage since this unit relies on you “seeing” the venting process so you can react by slowing down. Regardless, we carried out the test as planned using the standard “control fill” and found that that this unit allowed the nozzle to click off just in time (we could see fuel rising in both the clear tube and fill level) with minimal spilling at 10 gpm. For the 20 gpm delivery, we saw fuel enter the tube but fuel rose too rapidly for the automatic shut-off nozzle to disengage, spilling out a few ounces onto the deck. Seacurefill does make a 2” model that we suspect would better accommodate larger nozzles and higher delivery speeds. The Seacurefill Fuel Recovery System can be purchased at BoatU.S. and West Marine stores and through internet and catalog sales.
In general, we found that while refueling at 10 gpm, the amount of fuel from the venting process wasn’t significant enough to trip the auto shut-off fuel nozzles. Many times, the auto-stop feature disengaged just as the fuel reached the top of the deck fill, so the spills were contained to only a few ounces. However, none of the devices tolerated the high-speed fuel delivery at 20 gpm and sometimes spilled as much as a cup or more from the deck fill. Fuel would often continue to gurgle up and onto the deck, even after the nozzle clicked off. Additionally, because these deck fills have integrated vents, the nozzle opening was snug which made them prone to misting the deck with fine droplets of fuel.
As with the inline separators, we’ve learned you should never rely on the auto-stop nozzle triggering off in time. You will want to use an absorbent fuel collar, bib or pad to catch droplets, but do keep in mind this will restrict your ability to see what’s happening in and around the vent area. Also, always fuel slowly as you reach the top of your tanks.
FUEL MANAGEMENT SYSTEMS
What They Do:
We obtained two complete FloScan units for testing on a 55’ Fleming power cruiser, our testing platform for these devices. The packaging came with DVD installation instructions, but to stay on the safe side, we took our test boat with twin 435hp Caterpillar 3208TAs to an authorized Fleming dealer who was at ease with installing these units. In fact, the dealer commented that all long range cruisers should be equipped with such devices.
The FloScan units replaced the boat’s existing tachometers in the dashboard of our Fleming. Fortunately, no cutting was needed. Installers just dropped the units in and hooked them up to the GPS unit and both the forward and return flow sensors below decks. In the dash, with black bezels and amber and green LCD backlighting, these units looked as if they were original equipment.
We were fortunate in that the Fleming was about to head down the Intercoastal Waterway from Chesapeake Bay to Florida, giving us an excellent opportunity to collect data on the FloScan units. We asked the boat’s hired captain, an experienced skipper, to keep a special fuel log we created for the 1,500 mile trip. In addition to maintaining a fueling record, we also asked the captain a series of questions about the peculiarities of readouts and experiences (positive or negative) at refueling time.
When given the pre-departure lecture on the use of the new units, the captain appeared unimpressed (and perhaps a little skeptical). His log book revealed otherwise, however: “This has been interesting and the first time that I have watched a FloScan this closely. I usually run at a speed the owner requests. The FloScan impressed us that the higher the RPM, the higher the fuel rate, and it goes up rapidly!”
The FloScan appeared to be a very valuable tool for determining fuel consumption and could be relied upon to determine the amount of fuel needed at the fuel dock. Although we had hoped for more precise data, the captain (who was primarily engaged in his job of delivering a boat, not our job of conducting a Foundation Findings test!) wisely used every means available to calculate the amount of fuel he needed. He noted in his log that he could “probably rely solely on the FloScan to determine fuel remaining, but I always choose to double check it with the clear sight gauges adjacent to each fuel tank.” And who can blame him in the middle of a long range passage?
What We Found
Now, here is the kicker --- remember that the captain stated that he usually runs the boat at the speed the owner requests? Suppose in this case, the owner requested the delivery captain to run the boat at 12 knots. That’s only two knots faster, but our calculations show he would have burned approximately twice as much fuel! For the test boat’s trip south, this owner would have spent an extra $4,000 in diesel fuel!
Although the FloScan is also a reliable tachometer and hour meter, its basic function is to calculate fuel consumed. It does not, however, calculate gallons remaining. We found this to be a bit concerning, as most all other high-end fuel computers do have this important feature. When asked, FloScan responded that they are working on adding new features, and may combine it with another software and chartplotter package so you can program your tank size, which will ultimately give you “range” or miles to go on fuel remaining.
The boat we had available to test this unit was a 21-foot Stratos center console powered with a single 200hp gas outboard. Since our application was for a gasoline engine, it had only one inline fuel sensor. Navman also offers models adaptable for 2-stroke, EFI and diesel engines ranging from 50-450hp. For the diesel units a second fuel transducer is included to subtract unburned fuel returned from the engine.
This unit was just over 9” tall and has a 7” vertical LCD display with fantastic resolution which allows for sharp definition of all screens, especially chart and sonar images. Our unit came with a multi-function bracket that allowed us to flush mount, dash mount or overhead mount it. We decided to dash mount it on a bracket that allowed us to swivel it. We noted the fuel sending unit was not much larger than a golf ball with a simple barb fitting on each end and a sending wire that returned to the readout display.
The only way to evaluate these features was to go for test runs, watch fuel consumption and monitor the readouts—then refuel the boat and do it all over again. On our first run out, we were impressed with how easy to read the screen was, even with bright sun light and inherent boat vibration. When in the full screen mode with a simple white background, the black numbers were easy to see all on one screen. There was no reason to scroll around or tab between screens, since fuel used, fuel remaining, fuel flow, fuel economy, boat speed and nautical range were all right there before your eyes. To the right of this information was a bar graph that serves as a fuel gauge. When your tank is full, the bar is all yellow. As you get closer to empty, the bar turns red and you will hear an audible low fuel alarm.
Since the fuel
computer just reports the flow of fuel rather than actually measuring
it in the tank, the first thing you must do is “calibrate”
it. All that is involved is telling the computer how much fuel you
have in your tank initially (as a baseline) and programming in how
much it holds so that it will know what to calculate in the future.
You must “reset” the Navman after every fill-up to keep
it updated/calibrated. Keeping it calibrated is critical to keeping
Over the course of our trials, we determined the flow rate to be accurate on this model and the fuel efficiency readings to be infinitely useful. We could adjust throttle and trim and in an instant be provided a new readout in response to our adjustments. Raising and lowering trim tabs and even sending passengers forward or aft would alter the efficiency in nautical miles per gallon (NMPG) and flow rate.
Range was something
that was a bit intriguing to us. At idle and with a full tank of
gas, our range was 4,000 miles! Of course, our flow rate was only
a tenth of a gallon an hour. At full speed, our range was drastically
less and more fathomable for a vessel of this size. In short, the
range was all over the board since it was directly tied to speed.
Additionally, since range is tied to NMPG and a functional GPS,
good GPS signal strength is a must. The fuel functions are all tied
to the flow meter function, and the rest is pretty much a simple
internal mathematical calculation, with no guesswork for the captain.
Furthermore, a fuel computer can actually serve as a diagnostic tool. For instance, a decrease in GPH could indicate a problem in one of the engines such as a blocked fuel line, spotty injectors or fouled fuel filter. An increase in GPH could indicate other health issues such as improper firing, bad ignition timing or even a broken fuel line. An increase in both engines could mean a fouled bottom, improperly aligned shafts or nicked propellers.
For determining fuel level, we urge users not rely solely on the fuel computer alone. A prudent mariner will check and compare data with an in-dash gauge or a sight glass if available and will have absorbent pads ready when refueling. An experienced boater will also take into account other information including the feel of the helm, the wake and other cues to help determine peak efficiency and overall performance. A final note on fuel gauges. Resist the urge to check your in-dash fuel gauge while refueling your boat. It is a dangerous habit to have any electricity and charge flowing through your boat while dispensing fuel.
While testing inline fuel/air separators and vented deck fill fittings, our testing revealed that the Racor Lifeguard Inline Fuel/Air Separator (Model LG100) was the most dependable all around performer. We could rely on it to keep fuel from overflowing through the vent line and to keep backsplash from occurring up the deck fill. Because of its dependability, it earned the STAFF PICK for this series of tests. This oblong grapefruit shaped device (about $100 retail) may not fit in every boat, but where it will, we think it’s a good investment to make refueling a more worry-free event.
Throughout the course of our testing, we confirmed that there appears to be no one single answer to better manage fuel for each and every boat. Some boaters who buy large amounts of fuel may want to consider a fuel computer, which can quickly pay for itself when the boater is able to establish the most efficient RPMs and trim. For other boaters, a vented deck fill may be an option to help reduce overboard spilling, particularly if they are willing and able to slowly fill the fuel tank.
For everyone filling a fuel tank, there are also simple oil absorbent cloths, fuel nozzle donuts or bibs, and catchment devices to attach externally on the vent. These products are as useful for the marina fuel dock operator as they are for the individual boat owner. Learn more in our Clean Fueling Products Directory by clicking here (link to PDF of Fueling Directory—to come later- we’re waiting on Creative Services).
The bottom line: anyone with an engine in their boat can do something to keep fuel drops out of the water. Thanks for your help!
BOATS ARE NOT PRESSURIZED LIKE CARS!
Cars utilize a pressurized system to deliver fuel directly to engine injectors. This is done under high pressure delivered by a pump within the fuel tank to assure peak performance and economy. This type of system also does not permit air or fuel to escape from the tank during operation and does not have a vent to relieve pressure. Cars also have a carbon canister to control vapor emissions.
According to the Boat Safety Act of 1971, pressurized systems are not permissible for boats. If they were, in the event of a failure anywhere in the system, a large amount of fuel would collect in the bilge creating a very explosive situation. In addition, boats pound more while underway and fuel gets jostled, causing additional expansion. The pressure created must be released – and on boats, it is released though the tank’s breathing vent. Shake a can of soda and open the top and you’ll know the explosive answer as to why boat fuel systems aren’t allowed to be designed like cars.
WHY DO BOATS BURP?
When refueling rapidly or overfilling your fuel tanks, boats vent air that is often mixed with fuel. During refueling, gas goes into the tank and displaces air. The air escapes out through your boat’s fuel tank vent. When the tank is nearly full and there is no more air to displace, frothy fuel begins to bubble out into the water or onto your decks.
Additional expansion of the fuel (and subsequent leaks out of your boat’s fuel vent) may occur when cool fuel is pumped from underground storage tanks into the boat on a hot day, or during the rise and fall of outside temperatures.
For these reasons, you should never top off your fuel tank and you should always leave 10% of tank capacity for expansion. Also try to refuel when you are headed out, not when you are putting the boat away. Trailer boaters should take the added precaution to fuel their boats on a level surface, or air pockets can form in the tank that can lead to the burping or back splash of fuel.
GROUNDING ESSENTIALS and a SPECIAL WARNING:
A Caution About Grounding Your Deck Fill: Please check with your installation instructions regarding grounding requirements or refer to a marina or boat yard that is versed in American Boat & Yacht Council (ABYC) construction standards.
Because fuel nozzles are metal and the flow of fuel through it generates static, a small but dangerous spark (called an Electrostatic Discharge or ESD) can occur when the nozzle is inserted into a metal filler neck. To prevent sparking, a ground wire must be attached from the metal deck fill unit to the boat’s bonding system. Also, it is important that the nozzle remain in contact with the metal deck fill at all times while refueling. Never wrap a nozzle in an absorbent pad or rag so that it prevents a good contact between the nozzle and metal body of the deck fill. When refueling portable fuel tanks, always place directly on the ground, never on a plastic truck bed-liner or a dock made of synthetic plastic wood. Good contact between a portable tank and a solid grounded object is essential.
Special Warning for Plastic Body and Metal Fuel Caps: Deck fill units that have a plastic body with metal components such as a metallic lid or metal retaining chain, are NOT to be grounded. Read the important Safely Message & Technical Bulletin issued by the United States Coast Guard (USCG) in February 2005:
WHY ARE BOATS FUEL TANK GAUGES INACCURATE?
We wondered why so many boats have problems with fuel gauges so we asked around about why gauges seem to be inherently inaccurate. The response from manufacturers was “don’t blame the gauges!” Rather, the most common culprit cited was the sending unit (that’s why tapping on the glass rarely works)!
Most fuel gauges rely on a sending unit with a float that is often manufactured by a separate company. The float rises and falls with the fuel level and sends an electronic signal corresponding to a unit of measurement (usually ¼ tank increments) on your fuel gauge. Often, new boats are shipped on trucks when the fuel tanks are empty, causing the sender to bounce and become misaligned. Another potential reason for inaccurate readings is that tanks are often designed to fit the bottom contour of a boat and sometimes shaped like a triangle. This means that the sender and gauge must be compatible with unique tank shapes, and dropping in a stock sending unit is not likely to read accurately.
In addition to issues with the float arm and tank shape, there may be calibration, voltage fluctuation or grounding issues at play. The bounce, heel, trim and general abuse that a boat takes when operated affects proper readout as well. Have you ever come off a plane and suddenly have a different readout?
If your boat has some fuel gauge issues: 1) Manually inspect the sending unit in the fuel tank. Be certain it has no internal rubbing or an obstruction. 2) Check for proper voltage, wiring and ground connections and determine if the sender and gauge are compatible. 3) Visually calibrate by refilling your tank in known increments and make a few hash marks with an indelible marker right on your in-dash gauge at these intervals. This process will take some time, because you must return the nozzle to the pump and properly ventilate your boat (at least 4 minutes) each time before turning on the key to check the gauge to avoid a potential explosion.
Here is some additional information that you may find interesting. If you have questions, comments or would like to share some personal experiences or observations, please contact us.
Foundation for Boating Safety & Clean Water
©2007, BoatU.S. Foundation for Boating Safety and Clean Water