Who owned pilot ship Wyuna in 1970's
 

Hi, I am trying to fill in some history of the ship below which served 30 years as a pilot vessel for Australian Port Phillip Sea Pilots.
O.N. (official number): 177243, Ship Name: ‘Wyuna’, Port: Melbourne, No. / Year registered: 2 / 1954.
The official history is that the Sea Pilots owned it until 1979 when they sold it to Australian Maritime College in Launceston Tasmania, but they swapped to fast launches in 1972 and I believe it was sold to a private owner then before it was sold again to the Maritime College.
Would anyone know how to find out the ownership of the vessel from 1972 to 1978?