Finally got the parts from Atlanta Marine . The instructions say to run a 1/2''x 13 tap through the base to clean up the threads and the insert can be screwed in by hand.
Good luck with that. The threads on the insert are not cut deep enough to just screw in it wont even start. I had to recut the threads on the insert also . After repeated attempts and trial fits I finally got it seated and the locking pins secured . I was told that SC doesn't use the XTP tower any more . Probably for the best my experience with both Atlanta Marine and XTP has been a week of aggregation poor to no customer service and bad engineering. All of this was caused by not informing the customer that the tower knob threads have to be covered with Anti seize.