What statement is true concerning...

🔍 Key Concepts

• Stern tube bearings support the propeller shaft where it passes through the hull and are exposed to sea water at the aft end and to the engine room at the forward end. • On oil-lubricated systems, seals have two roles: keeping sea water out and keeping oil in. • Think about which end (forward vs aft) is closest to the sea and which is closest to the engine room oil system.

💭 Think About

• Visualize the propeller shaft running from the engine room, through the stern tube, out to the propeller. Where is the sea water located? Where is the oil sump or header tank located? • For each seal (forward and aft), ask: Is its primary job to stop sea water from entering, to keep oil from escaping, or both? • Compare each choice: Which one correctly matches the location of the seal with what it needs to keep in (oil) and keep out (sea water)?

✅ Before You Answer

• Identify which end (forward or aft) is at the sea side near the propeller and which is inside the hull/engine room. • Confirm that sea water only exists at the aft/outer end of the stern tube, not at the forward/inner end. • Make sure one part of the statement correctly describes preventing sea water ingress and another part correctly describes retaining lubricating oil in the bearing.

What statement is true concerning oil-lubricated stern tube bearings?

The forward and after seals are both designed to prevent the ingress of sea water and the after seal is designed to retain the lubricating oil within the bearing.

The forward and after seals are both designed to prevent the ingress of sea water and the forward seal is designed to retain the lubricating oil within the bearing.

The forward and after seals are both designed to retain the lubricating oil within the bearings and the forward seal is designed to prevent the ingress of sea water.

The forward and after seals are both designed to retain the lubricating oil within the bearings and the after seal is designed to prevent the ingress of sea water.

🔍 Key Concepts

💭 Think About

✅ Before You Answer