It is not advisable to use concentrated heating or wedges and jacks to remove a sleeved keyless propeller due to the risk of damaging the propeller, shaft, and their contact surfaces. The recommended method involves using a hydraulic pusher system which applies a controlled force to safely and efficiently remove the propeller.

(i) Expansion of Boss by Intense Concentrated Heating by Blow Torch

Using a blow torch for intense, concentrated heating of the propeller boss is risky because it can cause uneven expansion, leading to stress cracks in the propeller or shaft. This intense heat can also damage the material properties of the propeller and shaft, reducing their strength and fatigue resistance. Furthermore, uneven heating can warp the propeller, making it difficult to reinstall correctly.

(ii) The Use of Wedges or Jacks

Using wedges or jacks is also not advisable. This method can exert excessive, localized force on the propeller boss or shaft taper, which can damage the critical contact surfaces. Additionally, there is a risk of slippage if the wedges or jacks are not positioned correctly, causing sudden, uncontrolled movement that could harm the propeller or shaft. Using this method can also lead to improper alignment during removal and reinstallation.

Hydraulic Pusher System

• Pressurised oil is injected between the propeller boss and the shaft taper via drilled oil passages.
• The oil film creates a separating force that safely and evenly pushes the propeller off the taper.
• This method ensures controlled, damage-free removal without excessive mechanical stress.

Alternative systems:

• Mechanical pusher system: Specially designed bolts or a pushing device apply gradual, uniform force to separate the propeller from the shaft.
• Split liner system: A thin metallic sleeve is inserted between the boss and shaft to aid separation, often in combination with hydraulic or mechanical pushers.

Additional key points about sleeved keyless propellers:

• No key fitted: Torque is transmitted solely by the interference fit between the boss taper and the shaft taper.
• Material properties: Propeller bosses are often made of bronze, which has a higher thermal expansion coefficient than the steel shaft—temperature changes must therefore be carefully controlled.
• Push-up procedure: Installation involves a measured push-up distance to ensure correct interference and secure grip between boss and shaft.