White Star and Harland & Wolff had decided from the start of the ships design that they were not going after record crossing speeds and compete with Cunard on speed records. They were looking at speeds of 21-24 nautical miles per hour rather than speeds of 26-27 knots. One of the differences that White Star saw as a benefit was they used less coal to cross the ocean than Cunard did.
The whole propulsion system of the Titanic was far more complex than I had thought possible in 1912. Based on information on the web site titled “Titanic’s Prime Mover – An Examination of Propulsion and Power”(1) the 29 boilers and 3 primary steam engines provided 59,000 horsepower. This equipment required over 450 men to keep it running 24 hours a day for up to 8 days.
I was looking at this site to try to find out how these engines were operated on the evening of April 14 as the bridge was dealing with an iceberg dead ahead. This article indicated that if the men were in place ready to take action (they were not on April 14) they could stop the primary reciprocating engines in 60-90 seconds. They would need an additional 60 to 120 seconds to get the propellers turning in reverse at the speed indicated by the bridge telegraph. This may be why there seems to be some confusion if the ship was actually moving in reverse in the few minutes after the iceberg was sited.
In one article I was able to find information that the time from reporting the iceberg and hitting it was 37 seconds (2). Based on the information on how the Titanic engines worked by the time of impact the best that the engine room would have done was begin the process of stopping the reciprocating engines. The slowing of the engines would have cause the propellers to provide small slowing effort as they dragged through the water.
I didn’t consider the centre propeller, driven by a turbine engine, as it didn’t have the capability to revers it’s rotation.
I did find a reference to the sea trials of the Titanic where they did an emergency stop with the ship. I assume (with care) that they used the reverse capability of the two reciprocating engines. In this case it took about 1/2 a miles to stop. The ship’s chance to stop before hitting the iceberg is very unlikely on the evening of April 14.
Reference
(1) Steam Power System on the Titanic
(2) https://www.thoughtco.com/little-known-facts-about-the-titanic-1779209
Titanic a Tragedy 