Spill? What Spill?

Products to Keep Fuel Where it Belongs — In Your Tank

March 2005

It’s hot, the harbor is crowded, and you have been circling the fuel dock for 25 minutes waitingA fuel dock is open for service and has vessels 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 are not the only one.

The Issues

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. (Learn more about why boats “burp.”) 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.

An illustration shows the numerous types of inline check valves for fuel vents.Couple that 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 a sheen on the surface of the water. And by creating a sheen, you are breaking a law and opening yourself up to fines that can go into five digits. While you want to get rid of the sheen, it’s also illegal to use a couple of squirts of dishwashing detergent on the water’s surface. Add this all up, and you can see how the nature of boat fuel tanks and the law don’t exactly make compatible bed fellows.

Whether it’s your concern over the environment, worry over landing a fine for pollution, or your quest to keep caustic chemicals off your teak and gelcoat, you’ve probably got a vested interest in keeping your fuel’s journey from nozzle to tank a clean and simple one. So how do you do that?A display is set up to test the various types of fuel fills.

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 that can 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 other supplies that can come in handy while fueling any boat. Finally, there are some tried and true techniques for fueling that will reduce the chances of overfilling. The end result of all this research is that we found there’s an option for every single boater. We hope this information will help you find the right answer for you.

Testing Protocols

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 A red fuel pump is fashioned for our tests.shore-side 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.

The Mock-up: To test these hardware options, we assembled a mock-up of a boat’s hull, deck fill, tank and tank vent according to American Boat and Yacht Council (ABYC) construction standards. We used certified United States Coast Guard (USCG) components including an 11.5 gallon fuel tank and approved hoses. Then we installed the various deck fills on the “deck” of our mock-up. Below decks, we had good access to easily change the various inline devices. We did not test any combination of devices. In other words, we did not use an inline separator and a combination deck fill and vent at the same time.

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.A tester prepares a solution of soap and water for the test.

The Nozzles: To test our devices, we obtained fuel nozzles from a marina distributor and powered them with an electric pump. We used a standard ¾” nozzle that delivered 10 gallons per minute (g.p.m.) and a high speed 1 ¼” nozzle that delivered 20 g.p.m. to replicate the flows found at the fuel dock.

The “Fuel”: 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 gallons of water for “gasoline.” For our “diesel” mixture, we added ½ teaspoon of car wash soap to 15 gallons of water because of diesel’s greater foaming characteristics. It was essential to get these mixes right, or we couldn’t expect the devices we were testing or the automatic shut-off for the fuel nozzles to work properly.

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.

Inline Fuel/Air Separators

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.An image of an inline fuel / air separator

Racor Fuel/Air Separator for GAS OR DIESEL

(Model #LG100; retails for $109.99) At first, we balked at the size of the LG100 (about the size of an oblong grapefruit). It was the largest of the units tested and we had just enough clearance to install it. But once installed, it worked each and every time on our mock-up and our loaner boat. When the tank became full, it allowed the automatic shut-off on the nozzle to disengage in plenty of time without venting fuel over the side or causing backsplash from the deck fill—with not one spill! We feel that because of its large size, it acted like a reservoir, allowing for additional room for fuel expansion. The larger size of this unit also provided the opportunity for fuel to settle before returning it to the tank and giving the nozzle time to click off. It works well with either gasoline or diesel and was the only product in our testing line up that could be taken apart if necessary. For these reasons, the Racor LG100 was the STAFF PICK for Foundation Findings #40. It can be ordered through West Marine stores, Internet and catalog sales.

Racor Fuel/Air Separator for GAS ONLY

An image of an inline fuel / air separator on display for our test.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 the overboard 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 West Marine stores, internet and catalog sales.

Attwood Fuel Vent Line Surge Protector

An image of an inline fuel / air separator by Attwood brand.(Model #1675; retails for $23.99). This was the smallest of the inline devices we tested, about the size of a roll of quarters. This device is a gasoline-only model (no diesel model is available), but we were told by the manufacturer it is compatible with diesel as well. However, when we tested it with the soapy “gasoline” mixture at 10 gpm, this device did not allow the nozzle to click off in time and fuel bubbled from the deck fill and overflowed onto the deck. When we tested this device at 20 gpm, it “overpowered” the unit causing some minor spillage through the overboard vent, and a significant amount of backsplash from the deck fill. In fact, during our onboard boat test later, we witnessed a column of fuel about three inches in height and two inches in diameter shoot up from the deck fill when the tank became full. In both testing situations, the device made some gurgling noises to indicate a rise in fuel, so a prudent mariner should heed this audible cue and slow down. This product is available at West Marine stores, internet and catalog sales.Attwood brand p-trap fuel surge protector

Attwood 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 were that as the unit suddenly prevented fuel from escaping overboard, backsplash from the deck fill occurred. With high speed fuel delivery, the pressure even slightly “overpowered” the unit, causing a simultaneous leakage of fuel overboard from the vent and fuel overflow on deck. The Attwood P-Trap Surge Protector is available through the West Marine catalog sales special orders department.

Inline Fuel / Air Separator Summary

We discovered a very disturbing trend with most of the inline devices tested. For most of the units, pumping at 10 gpm until the automatic shut-off nozzle clicked off caused fuel to bubble over the mock-up’s deck. The results were even more disastrous when we pumped at 20 gpm. Due to the sudden blockage of the vent by the rising ball in the inline separators, fuel (mixed with air), was then forced out of the actual filler hole!

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

A young lady fills the fuel tank on her center console boat.Combination deck fills and vents, or vented deck fills, literally combine the fuel vent (that usually vents overboard) with the deck fill. Essentially, the vent line is redirected into the neck of the fill allowing vented fuel to return safely to the tank. When these units are installed at the factory, there is no need for an overboard vent. However, if you choose to install one of these devices yourself you must seal off your existing overboard vent so that water does not condense or siphon into your boat.

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 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.

A special note on installation: Some models require a ground wire to prevent sparking when a metal fuel nozzle is inserted. For grounding requirements please refer to the manufacturer’s installation instructions for specific details.

Attwood Angled Vent Deck Fill

(Model #3682; retails for $59.99). The Attwood Angled Vented Deck Fill features a hinged plastic cap and a stainless filler An Attwood bran angled combo fill/vent wth flip topneck with an integral vent and splash guard to prevent spills. The angled neck of this model allows for various installation orientations, including an An Attwood brand angled deck fill in the open positionangled surface. We chose to mount it on a 45 degree angle which allowed for good visibility to see the internal vent (which is inside the filler neck) when refueling. This gave us the comfort of looking around the inserted nozzle for hints that the tank was nearing capacity.

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.A fuel fill made by Perko features a flip top instead of the standard screw top.

Perko Combination Fill & Vent Set

(Model #1319; retails for $20.99). Perko offers many styles of vented fills for gas, diesel and water. The model we tested was a black A deck fuel fill on display in the open position.plastic deck fill with a hinged “flip top” opening that did not require a deck key and was clearly labeled “gas.” Because it was hinged, the lid could not roll into the water but we did worry that when open, someone stepping on it could break it. Since this model is all plastic, no special ground wire was required.

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.

Perko Combination Fill & Vent Set

A Perko combination fill and vent set in the closed position(Model #0541; retails for $28.99). A Perko combination fill and vent set in the open positionThis Perko product featured a round polished chrome cap and a plastic body. The cap has a beaded stainless steel retainer chain which is attached to the inside of the neck, making a snug fit for the nozzles. The tight fit blocked our view of the vent, so we couldn’t observe the venting process as it occurred. Additionally, the tight fit caused misting on the deck as we noted with other units, especially at the higher velocity. A ground wire is NOT recommended on this unit because of its plastic body and the possibility of an electrostatic discharge.

 

Note: The United States Coast Guard and the American Boat & Yacht Council (ABYC) are concerned enough about the possibility of sparking that as of 2/10/05 they have issued a Coast Guard Warning & Technical Bulletin for safe installation.

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 West Marine catalog sales special orders department.

Seacurefill Fuel Recovery System

(1 ½” Model; retails for $139.00). The Seacurefill 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.

Seacurefill fuel recovery system captures any overflow and routes it back into the fuel fill.Seacure fuel recovery system in the closed position.Seacure fuel recovery system in the open position.

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.

STAFF PICK: For cost, convenience, and reliability, our staff chose the Racor Fuel/Air Separator as the best venting product tested. Whether its a small tank on a sailboat or a large tank on a powerboat, we think it would work well They retail for a little over, $100.

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.

 

Vented Deck Fill Summary

The vented deck fill is a good concept, but we only recommend these products if you use them with caution. The vented deck fills did not promoteA failed test of the fuel fill system shows soapy water (representing fuel) splashing out of the fuel fill. backsplash as much as some of the inline separators did, but we were surprised by the fuel that found its way onto our decks. In general, these devices have a slight advantage over the inline separators: if you move the Another demonstration of a failed fuel fill-up.nozzle over to one side, you may be able to see when the unit begins to vent into itself and slow your speed of fuel delivery. The Seacurefill gives the most visible cues since clear tubing allows you to see precisely when your tank begins to vent, signaling your tanks are full.

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

When polling boaters for our Foundation Findings, we found that many were curious about how to increase their fuel efficiency and range of their boat. Furthermore, several respondents didn’t know with certainty how much fuel their tanks hold, while others complained their gauges were inaccurate. So to learn more, we obtained fuel computers from two manufacturers to find out if they could help boaters become smarter while boating and manage their fuel more efficiently.

What They Do:

The simplest of fuel computers can be purchased for under $200 and will keep track of basic fuel usage. The more advanced models not only tell you real-time gallons per hour fuel consumption, but indicate the total amount you have burned, and even better, how much fuel you have remaining. The very best fuel computers are integrated with your GPS and calculate your nautical miles-per-gallon (NMPG) giving you a true read-out of your efficiency. One model we tested even gives your projected range, essentially telling you how many miles you can go with the fuel remaining, at your current speed.

How They Work:

Simply put, fuel computers monitor the flow of fuel through fuel lines en-route to your engine using an internal paddle wheel and infra-red counter. For gasoline engines, this is straight forward and uses just one flow sensor installed somewhere after your primary filter. In the case of a diesel engine, an additional flow sensor is added to the return line, essentially subtracting the returned fuel from the delivered amount to give you flow rate. If operating two engines, select a manufacturer that offers a tandem engine readout/display or you can purchase a unit for each engine.

FloScan Fuel Flow Monitoring System

(Series K9000/GPS Interface; retails for $1,399.99). FloScan has been making flow sensors since the 70’s when the airline, trucking and shipping industries had a great need to conserve, evaluate and manage fuel use. With gas prices going up regularly, and with the great majority of recreational An image of the Flow Scan fuel flow gauge.boats being powerboats, it only made sense for FloScan to tap this market as well. FloScan makes units for both gas and diesel engines, either single or twins – ranging from 20hp to 4300hp and are available through the BoatU.S. or West Marine catalog sales special orders department, or bought directly from the company.

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.

FloScan Tests

We had hoped to just find out if fuel computers could be an accurate tool for avoiding overfilling, however once the data was collected, we discovered we also had a wealth of information relating to efficient fuel consumption, an area that presented surprise after surprise.

We were fortunate in that the Fleming was about to head down the Intercoastal Waterway from Chesapeake Bay to Florida,Image of a dashboar containing 2 floscans for 2 engines. 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

While we didn’t get definitive data on fueling accuracy, what we did learn was pretty amazing. With all the fuel data displayed right in front of you, it takes just a short while to determine what trim and throttle settings your boat likes and which are most efficient. For instance, based on what he saw, the captain of the Fleming identified 2,000 RPMs as the “sweet spot.” This equates to 7 GPH per engine (totaling 14 GPH for both engines) at a speed of about 10 knots.

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.

Navman Trackfish 6600

(Chartplotter, Fishfinder & Fuel Solution; retails for $1,899.99). Navman, a division Brunswick, the world’s largest marine company, has been delivering marine consumer electronics for 16 years. With a design focus on simple screen navigation and intuitive functions and options, the Navman won us over rather quickly.A navman trackfish display looks similar to a traditional fish finder. Navman provided us a TrackFish 6600 for testing with a few words of advice on installation and promised us if we only had room for only one instrument on the dash, this was it.

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.

Navman Tests

Our first test was to install the Navman. Since our FloScan was professionally installed, we decided to give this one a try ourselves, after all, there was no engine room claustrophobia to deal with and the fear of gouging a rosewood dashboard with an errant turn of a screwdriver would not present itself on this project. As promised by the directions, installation was a snap. After that, we set out to determine if our fuel computer was really worth the effort (and the money) for a boat this size and if it could prevent accidental fuel spills.A Navman fuelflow 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 it accurate.

What We Found

If all you are looking for is a fuel computer, you can get a Navman (either for gas or diesel) with all the fuel features, including a low fuel alarm starting at about a tenth of the price of the fully loaded combination chartplotter/fishfinder we evaluated. However, with all the features combined, we can’t deny it’s a great value.

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.

Fuel Management Systems

Testing the fuel computers reminded us of how expensive “fueling” our hobby can be, but they were a real eye-opener as we learned all sorts of tricks to make our boat go further on a single tank of gas. They can really be construed as the “must-have” gauge for your boat. They are rather simple devices that do not rely on sophisticated moving parts. They not only help track on board fuel usage and how much you need at the fuel dock, but also help reduce fuel consumption and increase your range.

An example of a fuel flow circuit output.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.

Some Solutions

This Foundation Findings allowed us to delve into a wide array of products, information, and techniques to help prevent small fuel spills and to better manage our fuel. It also reacquainted us with products that we can use on the fuel dock to help stop those drops and drips.

An attentive boater fuels his boat.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.

Top Tips for Refueling Your Boat
  • Know how much fuel your boat holds and how much fuel you need.
  • Turn off engine, electronics, and extinguish all open flames, such as stove or cigarettes.
  • Close hatches, ports and doors.
  • Put passengers ashore during fueling.
  • Use someting to catch spills out of the vent.
  • If you use a portable tank, remove it from the boat and fill it on the dock.
  • Use an absorbent pad or donut around deck fill to catch spills.
  • Maintain contact between nozzle and deck fill.
  • Hold onto the nozzle when refueling - don't use the hands-free clip.
  • Fuel slowly, and listen for a change in tone as the tank gets full.
  • Resist topping off - fill tanks to 90% capacity.
  • Have absorbent pads ready.
  • Do not use detergents to disperse spill.
  • After fueling, turn the blower on for 3-5 minutes.
  • Sniff bilges, the blower exhaust, and engine compartment for gas fumes.
  • Go Boating!

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.

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!

This project is part of our ongoing national clean fueling campaign: Help Stop the Drops. If you have ideas, questions or comments about this information, feel free to send us an email at safeboating@boatus.com.

More Information

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 Coast Guard Warning: Fuel Fill Technical Bulletin, or refer to a marina or boat yard that is versed in American Boat & Yacht Council (ABYC) construction standards.

Recent events have caused the boating industry to examine the policy regarding the bonding of plastic body fuel fills with metallic caps and retaining chains. Existing USCG & ABYC policy states that the bonding of these components is voluntary. A study by IMANNA Laboratories has shown that connecting the metallic retaining chain and cap of a plastic body fuel fill assembly to a boats bonding system may result in electrostatic discharge from a land-based fuel pump nozzle to the metallic components of the assembly when the boat is not in the water. This condition does not exist when the boat is in the water due to the equalizations of the ground potentials between the fuel pump nozzle and the boats bonding system. It is recommended by ABYC and the USCG that new and existing installations of this type of fuel fill assembly DO NOT INCLUDE any attachment to the boats bonding system. Existing connections should be removed from the point of connection to the boats bonding system to the fuel fill assembly. Removal of the metallic components of the assembly is not necessary; however, the U.S. Coast Guard and ABYC still require that METALLIC body fuel fills be bonded. For further information contact: John Adey, ABYC (410) 956-1050 ext. 29 jadey@abycinc.org Richard Blackman (202) 267-6810 rblackman@comdt.uscg.mil.
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 Boat 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 A boater refuels his pleasure craft.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.

If you have questions, comments or would like to share some personal experiences or observations, please contact us.