The ferry was the first of the fleet to be of all-welded construction and she is currently the last Mersey Ferry to be built. The Overchurch was popular with its Captains and Mates as its navigation bridge spanned the whole ship, rather than having a wheelhouse and side cabs such as Mountwood and Woodchurch used. A model of the ship by builders Cammel Laird is on display in the Williamson Gallery in Birkenhead. The wheelhouse was spacious with a single binnacle and brass wheel. Most of the ship's control instruments were fitted into specially-built stand alone units, including the telegraph heads. Unlike Mountwood and Woodchurch, there was no central set of telegraphs next to the helm, so the crew were required to move to either of the bridge wings to control the engines. Her bridge was modern, unlike the compact and relatively cluttered bridges on the Overchurch's two near sisters, where most of the instruments were attached to the bulkheads. It was a handsome vessel, with clean and smooth lines and a stout funnel. Her original livery was Birkenhead's orange and black, with a flame red band above the rubbing strake.
The Overchurch contained identical engines to Mountwood and Woodchuch, however, with a gross tonnage of 468, the ship was slightly heavier than its two near sisters and was therefore a little slower when running against a strong tide. The original plan was to have a third ferry built to the designs of Mountwood and Woodchurch, however, Birkenhead Corporation decided to design a completely new vessel.
Overchurch was fitted with a small deck area just behind the bridge and around the rakish funnel. The funnel was joined to the bridge at the front and was quite high, giving the ferry a top heavy look. There were also sheltering bulkheads beneath the bridge wings. When built, she was somewhat more advanced than the two sisters. As well as the completely enclosed navigation bridge, she also had a more advanced radio system, a loudaphone system and three window wipers. Her wheelhouse was also much warmer as she was enclosed, making it more favorable for the crew who did not need to venture outside.
The two medium speed Crossley diesel engines developed over 1,400 bhp combined and could easily propel the vessel over 12 knots against the flow of the tide. Both engines were controlled by Chadburn 'Synchrostep' telegraphs on the bridge. Like her near sisters, these were fitted with custom command dials which allowed for greater speed control ahead and astern and quick direction change by a 'brake' position which stopped the engines rapidly. Despite the concise level of control over her engines, she could be difficult to handle in strong winds. This was due to a design flaw which saw the front of her high funnel joined to the bridge. As such, airflow was blocked and this could create a 'sail' type effect under certain conditions meaning bringing her alongside could become troublesome. In addition, the flare of her bow was different to her two near sisters, her having a tendency to throw water over her forward observation deck in a strong swell.