oh yeah? You mean there was no transmission?
Correct. My first diesel tug was a direct drive unit where we had to stop the engine (using compressed air) and restart it in reverse (again using compressed air) to back down. Not the best boat to use for docking by far. I used to run car ferries in NY harbor between Brooklyn and Jersey City with such a boat back when the earth was young:
All of the steam driven tugs were direct drive by design, as are almost all steam driven vessels, regardless of whether they're reciprocating or turbine driven. The exceptions of course would be steam vessels that are driven by electric propulsion units driven by steam powered generators (think nuclear powered Naval vessels, ice-breakers, etc.).
Even the largest vessels afloat nowadays, such as the Emma Maersk and her sisters, which are powered by the largest diesel engines presently manufactured (the Wärtsilä-Sulzer 14RTFLEX96-C) are direct drive, although augmented by multiple electrically or diesel driven bow and stern thruster units.