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I own a 1988 Malibu Skier, and one of the things I've been thinking about upgrading on it is the fuel gauge. Specifically, I want to be able to have some kind of digital reading of how much fuel I have exactly left in the tank. Rather than having the needle gauge that moves as the boat rocks, is there a way to get a more accurate reading? One of my ideas was to have the sensor hooked up to a raspberry pi with the pi attached to a display on the dash showing the fuel level.

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    If the gauge is changing to show the fuel moving around in the tank, can you simply make a mental note of its low and high extremes, and evaluate a mid-point? – Weather Vane Feb 10 at 20:17
  • Does the tank contain baffles to help prevent sloshing? I thought it was a requirement on boat tanks, but really have no idea. – bob1 Feb 11 at 22:38
  • @WeatherVane You can, however my hope is to just be able to glance at the reading and know exactly where I'm at in any given moment. In my experience it gets pretty old having to watch the gauge and determine the midpoint. – kingderzelas Feb 12 at 23:12
  • @bob1 I'm not sure if it does, I haven't had time to take the rear seat off and look at it. My initial reaction is to say no. From what I know these older boats don't have baffles since they're carbureted monsters and sloshing isn't as problematic for carbs. Though that does make me wonder if installing an aftermarket baffle would solve the needle problem... – kingderzelas Feb 12 at 23:20
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I am not familiar with your specific boat. In most cases the reason the needle is moving is because the float in the fuel tank is moving as the fuel sloshes back and forth in the tank.

Changing to a digital readout is not going to give you more specific information.

See this related article. How to Test and Replace your Fuel Gauge and Sending Unit

  • With a digital readout you could add a running average filter to flatten the variation of the sensor reading. – Benedikt Bauer Feb 11 at 21:12
  • @BenediktBauer - and with an analog readout you put a simple low pass RC filter on it to average it out. Digital isn’t always easier than analog. – Jon Custer Feb 12 at 22:17
  • @JonCuster I've never heard of a low pass RC filter, but a quick google search shows something that could work. If I understand the concept right, it's a circuit that I can install and configure so that readings to the gauge that are too how or too low get ignored which results in the needle not moving as much. Ultimately showing you that average. My question though is, would that still only apply at one specific fuel level, or would the needle still average out as the fuel level drops or rises? – kingderzelas Feb 12 at 23:25
  • @kingderzelas - It would apply at all signal levels. The trick is finding the best time constant (basically the time to average over), but it isn't overly hard. If it takes an hour at full throttle to empty the tank, that is 3600 seconds, so a 10 second time constant should be just fine (a small fraction of time to empty, but long compared with bouncing around on waves). – Jon Custer Feb 12 at 23:35
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    @kingderzelas You could, but if you have too small an interval, then the noise from the waves or chop rolling/pitching the boat could affect the reading. For instance (theory only) if it takes 2 seconds for the boat to roll from horizontal and back again, then a 3 s interval would be too short, but a 5s or 10 s might be long enough to average out the readings. It's something you can play with by going out in the boat and seeing how long an interval is needed for the reading to stabilize under different conditions. – bob1 Feb 14 at 1:32

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