I have a 17' aluminum v-bottom, a 1974 70hp Johnson. Load = 2 batteries, 12 gals fuel, bait tank, tackle and 2 people. At WOT back off about 20% and run for 1 hour. It will suck a 6 gal dry. Is this normal? I have run a 14 pitch (25 mph) and a 17 (34 mph :D ) it didnt make any diff...