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A damaged propeller affects everything: speed, fuel, vibration and sometimes safety. Propeller repair underwater in Nagoya cannot do everything a workshop can, but it can fix a good deal of minor trouble and prevent small damage from becoming a large one.
Small nicks and burrs on the leading edge, bent corners and light scoring can be dressed by the Diver with grinding tools. The aim is to remove sharp edges and restore a smooth profile without changing the shape of the blade. The work is done within the limits set by the maker and the class society. Dressing is often followed by polishing.
Major blade damage, such as a large bend, a broken tip or a deep crack, cannot normally be repaired in the water. A bent blade needs heating and straightening in a workshop, and a crack needs welding and heat treatment. In these cases, the propeller must be removed, either in dry dock or, in special cases, in the water using lifting gear and a detailed plan. We tell the owner at once if damage is beyond afloat repair.
The propeller cone and nut are secured with locking devices. If a cap is loose or damaged, the Diver can check it and tighten or replace the fasteners. Loss of a cap can allow the nut to loosen, which is serious. A short inspection of these parts after any contact is wise.
On controllable pitch propellers, blade seals and the hub are important. The Diver checks for signs of oil leakage, damage near the hub and fouling in the blade bearings. A leaking seal may need internal work or a dock, but early detection helps. We report findings to the engineers, who can compare them with oil levels and pitch system readings.
A propeller wrapped in rope or net is a common problem. The Diver cuts and removes the material and checks for damage underneath. Even if the propeller appears fine, the shaft seal should be inspected, as the rope may have damaged it.
We inspect the propeller first and propose a repair method. Class approval may be required if the repair affects the blade shape or material. A normal dressing job takes 2 to 4 hours per propeller, more if several blades are damaged.
You receive video, photographs and a short report. The record shows the condition of the propeller before and after repair, which is useful for the technical file.
A rope guard, a nozzle or a Hull-mounted guard may protect the propeller on some ships. The Diver checks that these parts are intact and not loose. Damage to a guard often accompanies damage to the propeller. If a guard has been bent, the propeller must be checked even if no damage is visible from the deck.
A small nick that is left alone can grow, especially if the blade is under stress. Dressing a nick in the water costs far less than replacing a blade later. We advise owners to act on small damage while it is small.
Q1. What propeller damage can be repaired in the water?
Minor nicks, burrs, light scoring and loose caps or fasteners. Major bends, broken tips and deep cracks need a workshop.
Q2. How long does a propeller dressing job take?
Normally 2 to 4 hours per propeller, longer if several blades are damaged.
Q3. Can a propeller be removed in the water?
In special cases yes, with lifting gear, a detailed plan and class approval, but it is a major operation and is not common.
Q4. Why check the shaft seal after a rope entanglement?
Rope can cut into the seal lip and cause leaks even when the propeller itself looks undamaged.
