Barry, if you want to permanently pump 6 gpm, you can resize the pulleys and turn the pump slower. At 1250 RMP, the TSF2021 will make 6 gpm. Use this formula to figure your pulley needs. Engine speed X engine pulley diameter = Pump speed X pump pulley diameter. So....ES = 3400, EP = 3.5", PS = 1250. 3400 X 3.5 = 1250 X ?, 11,900 = 1250 X ?, 11900 / 1250 = ?, 9.52 = ?. Get it?