Ships were generally steamships in the 1930s, apart from a few sailing ships like the four-masted grain barque the Swallows see when returning to Harwich, one of the last of the old sailing ships .... the "Pommern" of Mariehamn (WD24).
The others prefer sail It’s the sails that matter says Titty, although Roger thinks a great deal about engines, he has a friend who thinks about nothing else. Roger says when John is rowing hard against the tide Now .... you’d be jolly glad if we had one (WD1). But when John (and Roger?) join the Navy they will be under (steam) power.
When Roger says But steam gives way to sail Jim Brading replies Not when sail's got plenty of room and steam's got none to spare. We've got the whole river to play with, and she's got to keep in the deep water channel (WD4).
Peter Duck the old Cape Horner dislikes steamships.
When they are going into port in the Hebrides, John says Steamer coming up astern and Captain Flint says Bit of luck .... that'll be the mailboat .... just time to get the letters done (GN8); she is pictured on the dustjacket and at the end of the chapter). But with the change of plans he tears up the letters.