🔍 Key Concepts

• Stern tube function and location on a vessel • Why stuffing boxes are designed to allow a small amount of controlled leakage • How water can act as both a coolant and a lubricant in rotating shaft systems

💭 Think About

• Think about what happens to the propeller shaft as it turns at high speed inside the stern tube—what problems could occur if it ran completely dry? • Why might engineers actually want a little bit of water to pass through the stuffing box instead of trying to make it 100% watertight? • Does that small flow of water have just one job, or can it perform more than one helpful function at the same time?

✅ Before You Answer

• Be clear on the difference between cooling and lubrication—can the same fluid do both in this context? • Consider whether the controlled leakage helps flush away debris or heat from the shaft and packing • Before choosing, ask: is the water performing only one of these roles, or is it serving multiple purposes simultaneously?