Question 16

The Correct Answer is B **Explanation for B (Air cranking motor.)** An air cranking motor (or pneumatic starter) uses compressed air, stored in a reservoir tank, to drive a turbine or vane motor. This system is highly common on auxiliary diesel engines found on fishing trawlers and other large marine vessels because it provides extremely high torque necessary to turn over large engines, is very reliable, and avoids the maintenance and complexity associated with large battery banks dedicated solely to starting (as required by electric starters). The illustration (MO-0044) would typically depict the robust housing of the pneumatic motor with visible high-pressure air supply lines connected, clearly differentiating it from electrical components or hydraulic lines. **Why the other options are incorrect:** * **A) Hydraulic cranking motor:** A hydraulic starter uses pressurized oil or fluid from an accumulator to power the starter motor. The visible connections would be high-pressure hydraulic hoses and return lines, and the system requires a separate pump/reservoir structure, which looks distinctly different from the air piping used in pneumatic systems. * **C) Gasoline engine cranking motor:** This method involves a small, separate gasoline engine (sometimes called a "pony motor") that is mechanically coupled to crank the main diesel engine. The illustration would show a complete, small internal combustion engine assembly mounted adjacent to the main engine, which is visually obvious and unlike the compact motor unit of an air starter. * **D) Electric cranking motor:** An electric starter relies on heavy-gauge electrical cables and a solenoid to power a DC motor. The illustration would show the distinctive solenoid housing and the large electrical terminals, lacking the necessary large-diameter piping associated with compressed air delivery.