I think this thread is drifting away from the original subject - let's stick to the subject, or as the Fench say:
revenons a nos moutons.
Some small boats have no rudder at all, they are controlled by changing the direction of the propellors. In Dutch: hek drive - what is the English name for it? So, you can't steer when the engines are idle. The small vessels in ShipSim seem to be of that kind.
When the rudder is placed behind the propellor, its effect is much weaker with no power or in reverse.
I have no experience with really large vessels, but in ShipSim I have no problems maneuvering both small and large vessels. Behaviour seems quite realistic to me. Besides, the really big ships in ShipSim are single engine (except the Titanic). So, what is actually the problem?