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The propeller and the rudder work together, and the damage that affects one often affects the other. A ship can lose speed, develop vibration or steer poorly long before anything shows on the bridge. A propeller and rudder inspection in Nagoya checks both in the same dive.
The Diver examines each blade from root to tip, front and back. He looks for bent tips, nicks and cracks on the leading edge, cavitation erosion, and any damage from rope, net or debris. The propeller cone, nut and cap are checked for security and fouling. The surface is graded for roughness by touch and by video. If the propeller is heavily fouled, we clean it first so the real condition is visible.
The rudder blade is inspected for dents, cracks, loose fittings and coating loss. The Diver checks the trailing edge, where cracks often start, and the bottom of the blade near the drain plug. The pintle and the rudder carrier area are inspected, along with the anodes. Where the design allows, the clearance between the rudder and the stern frame is measured with feeler gauges and compared with the maker's or the class limits, which are commonly a few millimetres.
Light damage is common: a nicked blade tip, a worn anode, a rope strand caught in the gap. More serious cases include a bent blade after contact with a quay, a crack at the trailing edge, or a rudder bearing that has worn beyond limits. Each is described with position, size and photographs, and we say plainly if the matter needs the surveyor's attention.
A damaged or fouled propeller can cost speed and fuel. Vibration at certain revolutions may be caused by a bent blade or a loose cap. Poor steering response can point to rudder wear. If the master or chief engineer has noticed any of these symptoms, please tell us before the dive so we can look in the right place first.
We need the ship's name, ETA, berth, Draft and the type of propeller, fixed or controllable pitch. Propeller and shaft must be locked and the thrusters isolated before the dive. A normal inspection takes 2 to 4 hours. If cleaning, polishing or minor repair is wanted, we can plan it into the same call and save a second visit.
Several signs point to propeller or rudder trouble. Vibration that was not there before, a drop in speed at the same revolutions, a rise in fuel use, a noise from the stern, or a ship that responds slowly to the helm can all have an underwater cause. After a grounding, a berth contact or a rope entanglement, an inspection is sensible even if nothing seems wrong. Catching a bent blade or a worn bearing early can avoid a much bigger repair later.
The report lists each blade, the rudder and the surrounding parts with photographs and short notes. It states whether the condition is normal, worn or damaged, and suggests a next step. If the finding is serious, we tell the master and the surveyor before the Diver leaves the water.
Q1. How long does a propeller and rudder inspection take?
A normal inspection takes 2 to 4 hours of dive time for one propeller and one rudder, longer if heavy fouling must be removed first.
Q2. What rudder clearance values are used?
Limits are set by the rudder maker or the class rules, and are commonly a few millimetres of clearance at the pintle bearing. We measure with feeler gauges where the design allows.
Q3. Can symptoms such as vibration be linked to the propeller?
Yes. A bent blade, a loose cap or heavy fouling can cause vibration or speed loss. A diver inspection can confirm or exclude these causes without dry-docking.
Q4. Does the propeller have to be locked?
Yes. The propeller shaft must be locked or secured and the thrusters isolated before the Diver enters the water. The chief engineer confirms this in writing.
