🔍 Key Concepts

• Direct-reversing main propulsion diesel engines on large ships and how they change direction • Common starting methods for very large slow-speed diesels vs smaller medium-speed diesels • Why large engines often use compressed air systems instead of electric or hydraulic motors

💭 Think About

• Think about the enormous size and inertia of a large, slow-speed, direct-reversing main engine. Which starting system can supply enough torque directly to the engine? • Consider how these engines obtain both starting power and the ability to start in either ahead or astern direction—what’s the simplest way to do that? • Ask yourself which systems are more typical for small auxiliary diesels and which for the main propulsion engine on big merchant ships.

✅ Before You Answer

• Identify which options are commonly used on small auxiliary or generator engines rather than large main engines • Consider which option allows admission of energy directly to the engine cylinders in the desired direction of rotation • Verify in your studies which starting system is standard for large, slow-speed, direct-reversing marine diesels on merchant vessels