Lowrance LMF - 200 Accuracy

[jlr]

I have just installed this gauge on my boat. Because I have twin diesels (with return lines) I am not using the fuel flow meters. I am however, relying on the remaining gallons page on the gauge to reasonably approximate what is left in my tank. Are these gauges reasonably accurate when used in this fashion (ie. with the existing wiring from the sender on the tank to the gauge)?

[emaier]

I have the LMF - 200 on my single outboard and found it to be very accurate until the flow sensor crapped out. Lowrance has sent me a new one at no cost.

Two observations on your application: 1. The LMF-200 can be set to show tank level based on fuel used (from the flow sensor) or based on the signal from your tank sender unit (with the EP-15 (fluid level sensor) between your sender and the LMF-200). Make sure you are set up for the latter because your fuel used measurement won't be accurate because of the fuel return plumbing. 2. Your fuel remaining reading from the EP-15 will only be as accurate as your sender.

[jlr]

Thanks. I am set up that way. However, to drill down a little deeper, and please, electronics guru excuse the misuse of terms, but I assume that the fuel sender on the tank sends some sort of electrical resistance measurement to the gauge and the needle on the old gauge (and the digital readout on the LMF) displays that electrical readout. The old needle gauge was not very accurate. I am hoping that the LMF will more accurately convert that electrical resistance reading into a digital display. Is that likely?

[mikeporterinmd]

The conversion from analog resistance to digital data would happen at the EP-15, not the LMF. Practically, I do not know if that makes a difference to you. But it might for troubleshooting purposes. For instance, if you saw inaccuracies, you would not look to the NMEA-2000 networking cables, but rather the EP-15 and tank.

Mike

[emaier]

If I recall correctly, the LMF-200 allows you to correct for the shape of your tank as well as correct for the fuel remaining. However, I think you must know how many gallons remain in the tank before you can make the correction. If your tank is rectangular, you set the LMF for three points (Full, 1/2, empty). When you know the tank is full, you enter into the LMF that the particular reading it is getting means the tank is full. When you know you have 1/2 a tank, you enter that into the LMF. This will account for the innacuracies in the sender signal. If you have a odd shaped tank, you would set the LMF for more reading points and when you know you have reached a certain level (i.e. 3/4, 1/2, 1/4), you adjust your LMF to recognize that value. Your difficulty will be figuring out when you have reached certain levels in the tank.

Do you possibly have a rectangular poly tank that you physically can note the fuel level? That would be too easy. There are other ways to figure it out, but are more of a pain. One would be to note when the LMF reads a certain level, remove the sender and use a stick to see if actual matches the LMF reading.

Good Luck.

Edgar

[jlr]

Edgar - thanks. Although I have a rectangular tank, I can't see in it. I may just have to try the hit or miss approach of fueling up at several different readings. I did the adjustment when the tank was full so that should help if the sender is at all accurate.