Push forward on the stick to accelerate, back to brake. If you go to a gun position, the gv will stay in the same gear and rpm (unless you hit a hill, in which case you should go back to the driver position and downshift.) Also in gunner position, use rudder controls to turn. Be careful, as trees and beach obstacles will kill you. In PT boats, the throttle is the speed control, but the rudder thing works in gunner positions.