🔍 Key Concepts

• Oil-lubricated stern tube bearings and how they differ from water-lubricated systems • Purpose of a shaft liner in way of the stern tube and seals • How bearing cooling and lubrication systems are normally arranged on large propulsion shafts

💭 Think About

• Think about what parts of the stern tube/shaft need protection from oil and seawater, and what component helps provide that protection. • Consider whether the stern tube bearing oil system is usually tied into the main engine lube oil system or kept separate, and why that might be important for reliability and cleanliness. • Ask yourself which statement sounds like a strict design requirement for all oil-lubricated stern tube systems, versus something that might only apply in special cases.

✅ Before You Answer

• Compare how oil seals work versus water seals at the outboard end of the stern tube and what operating pressures they can normally handle. • Verify in your textbook or notes whether a shaft liner is generally required in the way of the bearing and seal area for oil-lubricated stern tubes. • Check whether it is standard practice that every oil-lubricated stern tube must have a dedicated cooler or if cooling can be accomplished in other ways or shared systems.