nmea fuel usage w/ Lowrance elite 7 ti?

[LPowers]

MFD was showing 8.3 gallons remaining as I was flushing the motor after a day on the water and it ran out of fuel. I'm wondering if I have to put small amounts of fuel into it and run it out of fuel right when the MFD shows 0.00 gallons remaining? Then go fill the tank up and hit the calibrate option of the MFD.

[Moonlighter]

No, that is not the way to calibrate.

With that experience, you may simply have found out that while your nominal tank capacity is x gallons, you can only actually get (x - 8.3) gallons out of it!

The correct way to calibrate is as follows:

1. Fill the tank to full. Reset the system to a full tank.

2. Go and use at least 1/4 tank of fuel in one trip. The more fuel used, the better.

3. On your return, take a note of exactly how much fuel the system says was used. Then, immediately go and fill the tank again, try to go to the same gas station and the same pump. This helps ensure that the boat is sitting at the same angle, and that means you have a better chance to fill it to the same “fullness” as originally.

4. Take a note of how much fuel if actually took to fill the boat. Compare actual with predicted. If there is a variance between the two figures, you can then do the calibration process using the Elite ti.

5. Repeat this process if necessary 3-4 times at the most, you should then find that fuel used vs predicted is within 1% of each other. At that point, leave it alone, because the remaining variation is mostly due to filling the tank to slightly different “fullness” or because the boat is at a different angle at a different gas station.

It can also be due to evaporation, especially if the boat is left half empty for several weeks before refilling. You would be surprised to know how much more fuel evaporates off a half empty tank compared with one that is kept full.

However, as noted in my first para, this still leaves you with the uncertainly of how much fuel you can actually get out of the tank - ie, what it’s useable capacity is Vs its physical dimension based capacity. The only way to test that is first, get the calibration process done as detailed above, then run the tank out to empty, and see how much fuel the system says was used. Then, reset your fuel capacity in the system to match what you then now is the tank’s useable capacity.

cheers!

[LPowers]

Thanks moonlighter, looks like I may have been doing it wrong (quite a few times). Saying that, am I better off resetting the k-value to default, then filling,using,calibrating 3 to 4 times until I get close to actual usage? I've already found my actual capacity last year by accidentally running out of fuel and having to use my trolling motor to get back to the dock (85 gallons to fill it up until it puked so that's what I used as capacity on my mfd). I only go to one non ethanol fuel station every time and use the same pump.

[Moonlighter]

You could reset it and start again, especially if it is currently a long way wrong. Your call. Pretty sure there is a reset option in the Suzuki device menu in network.

Then follow the prcedure that I set out, and you should soon be good. I have found that once the fuel data is calibrated, it stays right unless something goes wrong with the network or interface software is changed or reset.

I set up a friend’s boat, we got it to 99.8% accuracy after 2 calibrations, and it never changed over the 6 years he had the boat. It was just uncannily accurate. He always filled the tank on the way home after trips. It was pretty normal for that boat to use 240 litres of fuel and for the fill to be within a cupfull or two of what the system said.

As I indicated above, evaporation is especially a factor when fuel tanks are left half empty - I didnt believe myself just how much can be lost due to evaporation, but a couple years ago we were having house renovations done and my boat was stuck in the garage with a half full tank for 4 months - I lost 15% of the fuel remaining and the only possible explanation was evaporation. I normally fill up on the way home after a trip, and never see a noticeable loss when its left with a full tank.

[LPowers]

With regards to evaporation rates, I was initially concerned about fuel going bad. I do use non-E fuel as well as Startron additive. My boating season in N FL is about 9-10 months. During that time I go through about 20 gallons a month normally. I wasn't sure Id cycle a full tank before it went bad. I was only putting in a little over what I thought I'd use that day. Maybe that's why mfd was showing 8.3 gallons left and WAY off(evaporation rate with that low of a tank). I took it out two weeks ago and ran it till it read 5.5 gallons remaining so something is off.