The term "heart of the ship" refers to a generator.
This lifeline serves as the foundation for all of the ship's operations.
The ship's generator needs special maintenance, care, and attention in order to operate efficiently.
Additionally, running a generator on a ship is a very different scenario.
A ship's generator needs a unique technique to start and stop, unlike the standard generators we use on land.
Even while the process isn't particularly difficult, it does require that a step-by-step plan be followed.
Every person on the ship makes every effort to avoid the "black-out," which can occur if even one step is missed in starting or stopping the generator.