I agree it has to be packing, in trying to picture an O ring in this application it may seem to fit but it would be directly in contact with the threads in the cap, installing the cap would probably tear it up. The set up HiDHo has is unique would be interesting to see it.
I did not have the boring tool needed so I had to send the heel piece out, it should be back later this week. With that I can put this thing back together.
This week its a new transducer, problem for another thread, getting the old one out,,,that%^& 5200
Thanks for the sanity check
OC earlier you said you do 1500 hours in about three years! I did 160 last year and considered it a busy season,,your out there a lot.