Have you seen the latest steering technology for stern drive boats? If you haven't you can preview a video demo here of the Volvo Penta sterndrive joystick system. Here's the video
Well overall it seems a nice toy to have, doesn't look cheap...
Couple of things re.the video; our hero 'Captain' is at one point going sideways towards the nearby pontoon at quite a speed, conveniently his arrival isn't shown...
Plus '"we can't go forward or back ( out of the berth ) so spring lines would be useless"; err, that's when spring lines are the answer...