I've had the same issue. For me, it happens only when the tank is less than 1/2 full...AND if I hit a wave pretty hard. All signs point to it's not a real issue, just a quick 'jolt' that the sensor gets for a moment.
The low fuel comes on at 1 gallon left and the engine will derate and only run at partial throttle when your down to a couple quarts. Thats what happened to me. I was surprised how far you can go just putting along at 20mph. I made it 5 miles back to the boat landing with the alarm beeping . If you do a lot of tail stands it will come on with 1/4 tank.I just ran my spark Monday. I forgot to fuel up before we went out, but it was after work so it was only going to run about an hour and it said half tank when I started her up. When I was about to leave I got a beep and a low fuel message. Gauge was blinking and it looked like it had two bars. I sat in the middle of the water for a minute and it stopped flashing and went back up to 3 bars. So my question is, do they start saying low fuel at 2 bars normally? How much fuel is left when you get the low fuel warning, anyone know? I had just read this thread the same day this happened so I thought it might be the same thing but rereading it I am not getting a defective message just low fuel.