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The propeller shaft is mostly hidden inside the ship, but the part that reaches the water is exposed to ropes, nets, fouling and wear. A propeller shaft inspection in Nagoya looks at the visible end and the seal area, and gives the engineers evidence to compare with their own readings inside the engine room.
Outside the hull, the Diver can inspect the propeller boss, the cone, the shaft end where it meets the aft seal housing, and the area around the stern frame. He checks for damage to the cone, loose fasteners, cracks near the boss and any sign of oil or water leakage at the seal. He also looks for fishing line, rope and plastic wound around the shaft, which can damage the seal lip over time.
Many stern tube leaks begin with something simple: a rope strand cutting into the seal. The Diver cleans the area, films it and, if needed, removes the wrapped material carefully. If the engine room has noticed oil loss or water in the oil, the video helps decide if the problem is external. It cannot replace the internal check, but it narrows the search.
When the engineers ask for it, the Diver can measure the gap between the propeller boss and the seal housing using feeler gauges, and record it against the ship's records. Comparing these values over time may show if the shaft is moving, which can indicate bearing wear. The exact method and limits come from the ship's manual or the class instructions, and we follow them.
Fouling on the cone and shaft end is removed during the inspection so the surfaces can be seen. If the surveyor or engineer requests polishing of the boss, we can do that in the same dive. Anodes on the cone are checked and replaced if they are worn.
Shaft work needs close cooperation with the engine room. The shaft must be locked, the turning gear isolated and the permit signed before any Diver goes near the propeller. A normal inspection takes 1 to 3 hours. Please send us the ship's drawings of the stern arrangement if you have them, and tell us what the engineers have noticed.
A seal that leaks a little can become a seal that leaks a lot, and a stern tube repair is expensive. Finding an entangled rope or a worn seal lip early gives the owner time to plan. It also helps the engineers decide if the problem is outside the ship or inside, so they do not open up equipment unnecessarily.
Please send the stern arrangement drawing, the type of seal, the date of the last seal change and any readings the engineers have taken, such as oil loss or bearing temperatures. If the ship has had a recent grounding or a rope entanglement, mention it. The more we know, the better we can focus the dive.
Q1. Can a Diver measure shaft wear?
A diver can measure the gap between the propeller boss and the seal housing with feeler gauges when requested, and record it for comparison. Internal wear-down readings are taken by the engineers.
Q2. How long does a shaft and seal area inspection take?
Normally 1 to 3 hours of dive time, depending on fouling and any entangled material.
Q3. What commonly damages a stern tube seal from the outside?
Rope, fishing line and plastic wound around the shaft are the most common external causes, as they can cut into the seal lip over time.
Q4. What must be done before the Diver approaches the shaft?
The shaft must be locked, turning gear isolated and a work permit signed by the chief engineer before any Diver goes near the propeller.
