Hi The Ionia. Avenger,Hibernia, Sun XXv and Sun XXVI were all converted in their later lives to the TOWMASTER Nozzle system of a fixed nozzle with three rudder blades. as none of them had had nozzles when built it made a marked increase in Bollard pull and manouverability, The Ionia for instance when built had a direct Reversing Polar engine which means the engine had to be stopped te enable it to run in reverse after moving the camshaft to alter the fuel timing, when converted to Towmaster gear she had a gearbox fitted as well which made ahead and astern much quicker,as the engine only ran in one direction.
Geo.