I have an older Ranger Bass boat (361V)that`s pushed by a 150 merc blk max that runs like a scalded dog.I don`t know what pitch the prop is but with just myself seated in it,and a flat calm lake ,it will do 50+.The previous owner told me he had opened the bores up on the motor.(what ever that means)Anyway, Everything on the instrument panel works just fine but the GAS gage bounces back and forth. Has anyone else had a similar experience with your gages? Is it an Electrical grounding issue?

Could be a grounding issue or a loose connection. The tank float mechanism is a rheostat that varies the resistance on the grounded side of the gage an could have some debris or trash on it. Does it bounce around sitting still? I would first check connections make sure they are clean and tight before running it almost out of fuel and removing the float.

Probably is the fuel sending unit. Mine was doing the same thing. It is a simple job to replace.

That is what I would guess too. My 375V has dual tanks and the left one stuck after the tank sat empty for a while. I filled the tank up and one day it started working again. I was just about to replace it. One nice thing about dual tanks is you know whether it is the gauge or the sender. That is unless both sender go bad at once.

I have a 92 361v. I was having that issue, so I replaced the sending units and it corrected the problem.