The problem is my stern drive wont shift into gear forward or reverse the engine revs up but no gears engage how do find out what the problem is ?I have already adjusted the remote cable and the shift cable and that worked when I was running on the boot but when I put the boat in the water nothing worked is it something simple or do I need to take it to shop? I've dropped the lower unit and replaced the impeller and shift shaft bushings o-rings etc what now?