Hi Bob,
Tricky subject you chose! The steam minesweeping winches installed in "regular" sweepers were very bulky and heavy, I don`t thing they could be refitted on the deck of a passenger ferry. However, John Lambert sells a set of drawings for these, you may wish to try his web site.
Motor gun boats used much smaller winches, which I suppose must have been electrically driven, but seem to be too small for such a big ship.
I agree with Davie in that probably a trawler winch would have been the best choice. For a picture of one, check the article on HMS SIR LANCELOT, right here at Model Boats, picture 6.
Hope this helps.