Fuel gauge.

[Mikered3500]

Took my boat out the other week for the first time. Filled the tank...or so I thought. The fuel gauge read full at 25 gallons, it's a rds 40 gallon tank...on the water the fuel gauge was jumping all over the place and now it reads below e full time now. I turn the key on and it jumps even lower....help .I'm not good with electrical diagnosis .any help would be greatly appreciated

 

[MTboatguy]

Sounds like you have a sticky float in the tank or corroded connections in the wiring to the gauge, I would clean all electrical connections then test again, but be aware floats get sticky over time and won't function accurately, depending on age, the float could also be fuel soaked and sank to the bottom of the tank.

 

[Scott Danforth]

float arm could have also broken off.

 

[alldodge]

What you working on?

Get a jumper wire to go from the sender lead (pink) on the gauge ground. Turn key ON and ground the sender wire, the gauge should peg Full.

If it does, go to tank sender with jumper and see if it pegs Full when sender is grounded.

If it grounds in both locations, you need a new sender. If it does not peg then its probably the gauge

If you think its the gauge and meter did not peg, then check for 12V on the purple wire and that you have a good ground on the gauge