HELP! Yamaha fuel guage reads correct on one tank and not the other?

[ShortSale]

HELP! Yamaha fuel guage reads correct on one tank and not the other? 1999 Grady White Marlin, twin 250's guage seems to be correct on when swicthed to one tank but when switch over to read other tanl guage either reads full or empty and doesnt gradually go down....i use the fuel flow total to accurately keep track meanwhile....any hints on how to troubleshoot? Maybee a bad sending unit from the fuel tank? suggestions aprreciated!

[rodbolt]

well if it works on one and not the other thats about all thats left. either the sending unit is bad or its wired incorrectly or a wire is broken. the sender should read between about 230 ohms and 35 ohms. it should vary when the arm is down at about 235 to arm up at about 35. at 5500 does it burn roughly 59 gallons an hour like all the rest . if the circuit is open the gauge will flash at you. sounds like the sender is sticking. be aware that when testing it takes several minutes at each point for the gauge bars to change. keeps it from scaling due to fuel slosh.