Main engine flywheel

What would happen to main engine if there was no flywheel?

The flywheel facilitates the continuous application of torque and smoothens the rotation of the shaft by storing energy in the form of rotational momentum.

So if we removed it, the torque would be applied erratically, causing higher amplitude torsional vibrations and more shaft fatigue.

Realistically, the engine wouldn’t last very long unless this was accounted for by design.