Lehman 120 tach adapter weeping oil

[f508]

I am getting a weeping leak from the port engine tach adapter.

I took it apart and the 2 part nut is tight to the crankcase adapter plate on the bottom, and the mechanism housing on the top. But the 2 part nut itself seems to be loose as though it is missing an O ring or something. Any ideas would be appreciated.

TIA!
Photos below wiped down and then after an hour run.

 

[Jbear]

Huh, I always wondered what that piece of Duct tape was over. I guess the PO removed the mechanical portion. Grrrr