Mike,
Here is 1 idea based on my personal experience with our boat which was new to us this year……….
Are you sure about the accuracy of the tank level readings? I have found that my “smartcrap” readings of gallons in the port and starboard tanks are not exactly “accurate” to the gallon. I have had to get used to the measurement inaccuracies and look at tank levels as more of a trend as opposed to an exact reading of “gallons in the tank before we left the dock MINUS gallons remaining when we get back to the dock EQUALS Fuel burned”.
In fact the marina spilled a little fuel at the beginning of the season because of the inaccurate tank reading. “Smartcrap” told me we had 10 gallons in the STBD tank and 50 in the port tanks, I told the marina to fuel the boat and even it out to 240 gallons total and expect to fill ~110 gallons on the starboard side and ~70 on the port side. it splashed over on the stbd side at 103 while pumping. Our boat is supposed to hold ~138 on each side, I only wanted 120 on each side so that we did not spill anything in the fueling process. We all learned something that day.
On an off day later in the season, I went over to the fuel dock at our marina and conducted an experiment. The marina was quite patient with me that day so I tipped the dock hands nicely. I filled 10 gallons per side at a time. At the end of each 10 gallon interval, we stopped fueling, I turned on the ignition(but did not fire the engines) and read the gallon levels on each tank and looked for any variation in reading based on measured fueling. Observations and Conclusions: The real world is not 100% accurate.
You may find some variation in reading in your tank at the different levels of fill. Experiment with it. I end up fueling our boat based on how much fuel I need for a particular run based on my knowledge of fuel burn rate. I put a little more in than I need as a prudent measure. I observe fuel level before the run then observe the fuel level after the run. Its kinda funny how different the tank readings are against what I would expect if things were 100% dead on accurate.
I would recommend running a few more fueling and burning tests to trend your readings. I would personally trust your instantaneous readings from the engines more than I would the exact gallon level readings from your tank. “Your mileage may vary”
As a general idea I would not trust 1 experience with numbers that are not quite what you expect. I would increase your sampling size and run a few more experiments to well and truly see if you have a real issue with your wiring or if this is just a matter of tank measurement accuracy tolerances.
Food for thought
Steve
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