knob

Hi all, Does anyone know where to pick up a replacement battery switch knob (the red one, that switches between 1, 2, both, and off) for the electric panel (in this case, for a 1984 E28)? I just took over a new boat, and this knob vanished somewhere in the past, and I don't want to be stuck...

I managed to back off the steering lock knob too far this weekend until it came off in my hand and now I can’t screw it back in. It seems there must have been some kind of fitting at the other end. The knob post is threaded, but has a channel cut into it near the tip. Is there a risk of the...