Not necessarily air in the system. Could be bad pumps/sticky valves in your helm. A good way to know if there is air in your system is to grab your motor and try to turn it. The steering piston should not move more than say 1/4”.speaking of boat issues. we lost our ability to turn left... sort of. i clearly have air in my hydraulic steering system that's not noticeable at idle speed. under power and the force of the water on the lower unit the wheel spins in circles to the left and takes FOREVER to eventually turn the boat. what a pain in the ass being offshore and you can't turn left. but we made it work and now we have fresh BFT.