gas consumption

Wanted to see what others had to say on this subject. I know theee boats rip through gas fast but I feel like something might be off with mine. So I go riding for hour. At full throttle my gas gauge is resting right on the left edge of the half tank mark. At idle same thing. Put on hoist...

I've tried to keep track but have been unable to determine roughly how many tanks of gas (15 ga) I can get out of one full reservoir (1.6 ga) of oil? Anyone figured this out?