From new in 1977 "Scillonian III" operated a year-round route through all weather conditions to service the cargo and passenger transport to and from Penzance and the island of St. Mary's, in the Isles of Scilly. At that time she would run a regular single daily service on weekdays leaving at 0915 from Penzance and then returning to Penzance from St. Mary's leaving at 1530. On Saturdays she was scheduled to run a double service leaving earlier in the morning and making a quick turnaround at lunchtime in St. Mary's and then performing a second return voyage in the afternoon. In 1990 it was decided to change the service and only run a seasonal operation. The Isles of Scilly Steamship Company Ltd. later purchased a smaller cargo vessel purely for freight and "Scillonian III" was put into maintenance and repair during the winter months.