boilers at a maximum pressure of . The engine was designed to give the ship a top speed of , but Monitor was slower in service. The engine had a bore of and a stroke of . The ship carried of coal. Ventilation for the vessel was supplied by two centrifugal blowers near the stern, each of which was powered by a steam engine. One fan circulated air throughout the ship, but the other one forced air through the boilers, which depended on this forced draught. Leather belts connected the blowers to their engines and they would stretch when wet, often disabling the fans and boilers. The ship's pumps were steam operated and water would accumulate in the ship if the pumps could not get enough steam to work.Monitors turret measured in diameter and high, constructed with of armor (11 inches in front at the gun ports) rendering the overall vessel somewhat top heavy. Its rounded shape helped to deflect cannon shot.McCordock, 1938, p. 31 A pair of steam-powered donkey engines rotated the turret through a set of gears; a full rotation was made in 22.5 seconds during testing on 9 February 1862. Fine control of the turret proved to be difficult; the steam engines would have to be placed in reverse if the turret overshot its mark, or another full rotation would have to be made. The only way to see out of the turret was through the gun ports; when the guns were not in use, or withdrawn for reloading during battle, heavy iron port stoppers would swing down into place to close the gunports. Including the guns, the turret weighed approximately ; the entire weight rested on an iron spindle that had to be jacked up using a wedge before the turret could rotate. The spindle was in diameter which gave it ten times the strength needed in preventing the turret from sliding sideways. When not in use, the turret rested on a brass ring on the deck that was intended to form a watertight seal. In service, however, this proved to leak heavily, despite caulking by the crew. The gap between the turret and the deck proved to be a problem as debris and shell fragments entered the gap and jammed the turrets of several s, which used the same turret design, during the First Battle of Charleston Harbor in April 1863. Direct hits on the