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FUEL MANAGEMENT SYSTEMS What
they Do
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. FloScan Tests
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. Navman Tests: 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. 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.
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