hi .. sorry for the late entry as i just saw this ..
I have a 2009 Bav 34 and I think your nightmare is is exactly what happened to me last summer .. suddenly, on hard acceleration fwd, i completely lost steerage. The chain (but not the wheel) had gone around so far that the turnbuckel tried to bend around the lower gear and broke. I grabbed the emergency tiller and was able to get to the dock and did have a spare chain on board, but wonder now how to prevent this from happening again.
Did you get anything useful from your post?