CL7 Freedom 235 engine display blinking fuel

[M1ke]

Hi
I can't find this in the manual- what does it mean when the fuel display is blinking? I of course understand that it means low fuel but how low? When you touch the icon to get more info, it fluctuates between 7% and 17%.

 

[Coastboater]

Not sure if ours are identical displays, but under an “information” selection there’s another called “tanks” that will also give you a % of fuel in the tank.
if you’re doing this underway or while the boat is rocking the reading is going to fluctuate due to the fuel moving around.

 

[seasick]

It means its time to gas up
By the laws of physics, and the nature of the hull's attitude, the level displayed on the gauge is not very accurate . Just moving yourself or a passenger aft or forward can change the displayed amount.
It is far more accurate to program and calibrate the CL7 for your specific tank specs and use the gas used figure to determine how much gas you have left. That also means that when you gas up, you need to reset the data in the CL7.

If you relay on the flashing level indication to gauge how much gas you have left, you will probably run out of gas some day.

 

[Hookup1]

I have older gauges that connect to the WEMA sending units in the tank. 8 bars will change with fuel level. The gauge debounces the sending unit with a several second delay. The bars are solid until you get to the last bar where it will start to blink. At this point you are very low on fuel and depending on the attitude of the boat could flame the engines out. Running bow up will get fuel to the back of the tank where the pickups are. Going slow will level the tank out and possibly be bow down depending on boat loading and move fuel to the front of the tank.

Unlike my cars where I can run them to 0 miles on the fuel management gauge you can't do this with the boat.

 

[M1ke]

Thanks! I agree on all; just want to know when it starts blinking , howl much is estimated remaining. I’m sure there’s a spec but I can’t find it anywhere.

It means its time to gas up
By the laws of physics, and the nature of the hull's attitude, the level displayed on the gauge is not very accurate . Just moving yourself or a passenger aft or forward can change the displayed amount.
It is far more accurate to program and calibrate the CL7 for your specific tank specs and use the gas used figure to determine how much gas you have left. That also means that when you gas up, you need to reset the data in the CL7.

If you relay on the flashing level indication to gauge how much gas you have left, you will probably run out of gas some day.

 

[seasick]

I don't know your year but assuming it has a 115 gal tank and the gauge works correctly AND the tank is relatively level to the water line, you probably have at least 8 gallons on the low estimate and 19 gallons on the high side. The key thing to note is that as mentioned, the angle of the tank to the waterline can make a huge difference in the reading.
When motoring the tank will read one level at rest and then read a higher number are the bow lifts up and gas moves to the rear of the tank. Likewise when you come to a stop and the bow sinks, the level read will drop. There is a delay (smoothing) to the level update, otherwise the gauge would be all over the place. Note also that the bottom of the tank sender, assuming a stick type unit) sits a 1/2 to an inch above the bottom of the tank. Therefore when your sender senses a zero level, there is still some gas in the tank. Whether or not you can use that gas depends on the angle of the tank and the actual depth of the pickup.
The stick type senders I am familiar with do not change in a continuous way but rather have incremental changes in output level. So two bars would represent a range of levels. The only time you can make a more accurate estimate of the tank level is if you are watching when the number of bars changes or starts to flash as in the one bar case.
All that aside, operating with one flashing bar is asking for trouble.

 

[Hookup1]

From what I understand the fuel sending unit is interfaced to the CL7. Correct me if I'm wrong.

On my boat the fuel gauge will blink when you are part way thru the last bar. With 8 bars on the gauge that means you are all the way down on the sending unit float. It knows where 1/8 of a tank is and that you are now below that level. The tanks have a V on the bottom that also has a flat bottom on it. This helps collect fuel when the tank is low. So bottom line is maybe 1/16 of a tank but only if you can pick it up and use it.



I don't have a CL7 but my Garmin chartplotter is interfaced to my engines. I get engine data like the CL7. The engine data page has a virtual fuel tank. You set the tank gallons and fuel level gallons. The chartplotter will get fuel burn information from the engines and adjust the fuel gauge on the engine data page. Add fuel to the boat and you have to tell the chartplotter how many gallons you added. I don't track my fuel this way - I use my other fuel gauge - but it is an option.

The sending units are a series of magnetic reed switches and resistors. As the float slides the resistance changes. But it's not linear - it's stepped. That "fluctuates between 7% and 17%" is probably the sending unit crossing one of the steps.

 

[seasick]

On my 208 with the command link gauges, one solid bar (when it changes from two bars to one bar) equals about 20 gallons in the tank. That is about 1/4 of a tank so the eight bars don't represent eights of a tank. When that one bar starts to flash, I have about 10 gallons of gas left but I almost never let it get that low. The tank is 82 gallons.
The 208 is somewhat light and just moving from all the way aft to the helm can at times decrease the reading by a bar or two. A half a tank when getting on plane (bow up) can make the tank look like it is full. You can't rely on the gauge when levels are low. I pretty much know what my burn rate is and how many gallons I use for a specific trip. When I need gas, I either add what I think I used up that day or add what I estimate will be used on the next trip with the end of day tank level at two bars minimum.

 

[M1ke]

thanks so much, helps me understand the system more than I did.

I don't know your year but assuming it has a 115 gal tank and the gauge works correctly AND the tank is relatively level to the water line, you probably have at least 8 gallons on the low estimate and 19 gallons on the high side. The key thing to note is that as mentioned, the angle of the tank to the waterline can make a huge difference in the reading.
When motoring the tank will read one level at rest and then read a higher number are the bow lifts up and gas moves to the rear of the tank. Likewise when you come to a stop and the bow sinks, the level read will drop. There is a delay (smoothing) to the level update, otherwise the gauge would be all over the place. Note also that the bottom of the tank sender, assuming a stick type unit) sits a 1/2 to an inch above the bottom of the tank. Therefore when your sender senses a zero level, there is still some gas in the tank. Whether or not you can use that gas depends on the angle of the tank and the actual depth of the pickup.
The stick type senders I am familiar with do not change in a continuous way but rather have incremental changes in output level. So two bars would represent a range of levels. The only time you can make a more accurate estimate of the tank level is if you are watching when the number of bars changes or starts to flash as in the one bar case.
All that aside, operating with one flashing bar is asking for trouble.