Previous owner said "antenna quit" so he installed a straight, non-retracting antenna mast. This screws onto a metal threaded post which extends out of black plastic tube. At first glance, this metal threaded post isn't original, but rather "rigged or screwed" into plastic tube (but I can't get it out). Otherwise I can't comprehend how a retracting antenna could pass through. Base of mast says Hirschman, but I'm still puzzled. Anyone have a close-up of antenna base (where it attaches to fender) so I can compare before I purchase new mast/motor?
Also, motor doesn't seem to make any noise, but with cover off, it appears quite clean inside. Fuse is ok. Any ideas?

1982 380 SL