Hydrostatic fuel gauge problem

[Karl]

I installed the dual temperature gauge in my 34 over the weekend and its really nice to know what the temperature is of the motor. I think the gas gauge needs some fettling however . The old gas gauge would only read 1/2 full but would hold at that level and drop as it should with use. The new one was set up as suggested and I can blow it up to read correctly but that level is not maintained. Over 8 hours it drops down to read close to zero . A drive will bring it up but it doesn't stay up - I'm thinking slow air leak - Agree? Karl