船舶主机冲车是指船舶主机的冲车，这是一种用于拆卸或维修船舶主机的专业工具。在英文中，它通常被称为"ship's engine crank"或"ship's engine crank handle"。

来源：在英文中，"crank"是指一种用于转动机械装置的手柄或曲柄，而"engine"则指船舶的主机。因此，"ship's engine crank"就是指船舶主机的冲车。

一些英文例句及其中文翻译如下：

The ship's engine crank is used to start the engine when it's cold. (船舶主机冲车用于在发动机冷的时候启动发动机。)

The ship's engine crank handle was broken and had to be replaced. (船舶主机冲车的手柄坏了，必须换掉。)

The ship's engineer used the engine crank to loosen the bolts on the engine. (船舶的工程师用主机冲车来解开主机上的螺栓。)