As my username suggests, I have my background in shipping. Started my professional life on the river Rhine as a deckhand, later first mate and captain. Later in service of the city of Amsterdam (portauthority, ferries). I worked with several engines of that time and still have a weak spot on them.
Last weekend I had the opportunity to join on a trip with the tugboat Elbe, formerly owned by Smit tugs in Rotterdam. The boat was first in service in 1958, later sold to the US Coastguard, later to Greenpeace and since a few years back home as active museumship.
With the help of many volunteers the ship has returned in it's original state including the original engines. It is driven by two 6cylinder Smit-M.A.N. engines of 1750Hp each. The two engines are connected to a shared transferbox, from there a single propellorshaft is driven.
The two engines can be engaged or disengaged via a pneumatic clutch, each engine can be started in forward or reverse. When manouvering there is one engine running forward and the other in reverse, whatever is needed the respective clutch is engaged. Once out on the trip both engines can be started forward to get the full 3500 Hp.
When not pulling the ship sails on one engine, for obvious reasons. I made a short vid of the running engine (partly with my phone) to give you an idea of these engines of the '50s. I thought I might share my weak spot.