noob needs help with mileage - only 10 MPG!

My slant never got good mileage but it was always a carb issue. Even with rebuild it wasn't great but still ran too rich at idle which I think was a bad float. I was tired of messing with it due too going with a 360 in a year. I run one summer with 8 3/4 with 3:23 and that killed mileage to the piont 360 gets better overall even with your foot in it a little bit. If your slant is in pretty good shape I would be suspect of the carb.