Instead of adapting an electrical sensor which may or may not provide accurate readings for your tank consider installing an hour meter. It will not only facilitate fairly accurate readings of fuel consumption and availability but will also help with engine maintenance requirements. In order to calculate fuel consumption and availability in tank all you need to know is the burn rate of the engine in hours and the size of the tank in gallons. A 2gm diesel burns under 1/2 gallon an hour on the average and if you have an 18 gallon tank you may safely surmise that your tank holds fuel for 36 hours. Fuel holding and usable fuel are two different things as the engine will start to suck air and quit before the tank can run dry. For navigation range purposes I would use 30 hours leaving 3 gallons in reserve. Once you have all this info all you need is to create a log and jot down the number of hours on the meter every time you fill up. Let's say you are going sailing one day and you want to know how much fuel you got left , take a reading on your meter and subtract the number on the log to see how many hours the engine has ran since last fill up. Lets say 8 hours so you know you have only used 4 gallons and hold 14 gallons in your tank of which 11 should be usable for 22 hours. Once you do the calculations they become easy and second nature. I have not found a more accurate and reliable fuel gauge than keeping tabs on your consumption. We took a trip recently on an h34 which had no gauge nor hour meter. We just made a point of keeping in our heads the motor run times per leg and after 10 days and some 500 nm we had the burn rate pretty pinned down at 0.65 gph. Whichever way you decide to go it is always good to know the burn rate of your engine and boat. You need not factor in currents, wind nor condition of hull as it is a simple formula, fuel used in gallons divided by time in hours. I don't break it down by engine RPMs as all I need is an average figure accordying to my motoring style, 95% of it is at cruising RPMs anyways.
