🔍 Key Concepts

• Purpose of stern tube and strut bearings on a ship’s propeller shaft • Properties of hardwood or rubber as bearing materials in a marine environment • Common ship practice for open, water-lubricated shaft bearings

💭 Think About

• Think about which lubricant is most compatible with wood or rubber when constantly exposed to seawater around the propeller shaft. • Consider what type of lubricant can be supplied in large quantity, is non‑toxic to the marine environment, and can also provide cooling. • Ask yourself which lubricant would practically reach the stern tube/strut bearings on an operating vessel without complex pumps or oil‑sealing arrangements.

✅ Before You Answer

• Verify which option is typically used for open propeller shaft bearings on conventional vessels. • Eliminate any lubricant that would be easily washed away or cause swelling/softening of hardwood or rubber. • Check which choice is commonly drawn directly from outside the hull rather than stored in tanks.