Fuel guage?
 

I've got the 47
Gallon tank in my 20sf. I've got a new guage and sender unit. The sender arm and float aim to the rear of the tank do when up the gas read higher and comes down when at rest or headway
If it aimed forward it would read lower
Is this set up wrong or just live with it ?

No it needs to point to the rear - there is a baffle in there as mine would stick on it sometimes - so shorter is better in this case. It will not be very accurate pointing sideways or to the front - I pointed mine sideways to test it and @ empty still had 1/4 tank