48" exmark sucking gas

[candk]

I bought a 48" lazer z v twin mower at back in july with the hopes it was going to be good mower. So far i have been highly disappointed it cuts horribly, never wants to start and its brand new. The biggest problem I have is that it sucks the gas I cannot go the full speed on the mower whenever i do a yard because it sucks the gas. I barely push the mower and still can only mow 7 yards on a tank of gas. this summer I mowed 40 yards a week and spent $180 in gas just in the mower. So I guess what im asking is anyone else having this problem with this mower and what can i do to get better gas mileage? thanks

[Spring Valley Lawn Service]

Figure gallons per hour. I got a 21 hp Kawasaki toro 48 inch z 400. I think I burn around 1.25 gallon per hour.