MST Marine Propulsion & Propeller Systems

Question 1

What is cavitation in a marine propeller?

Accepted Answer

The formation and collapse of vapor bubbles on propeller blades due to low pressure

Answer

Cavitation occurs when low pressure on the blade face causes water to vaporize, forming bubbles that collapse violently and erode the blade surface.

Question 2

What does propeller pitch refer to in marine applications?

Accepted Answer

The theoretical distance a propeller would advance in one revolution with no slip

Answer

Pitch is the theoretical forward distance the propeller would move in one complete revolution if there were no slippage through the water, similar to a screw thread.

Question 3

Which material is most commonly used for recreational boat propellers?

Accepted Answer

Aluminum alloy

Answer

Aluminum alloy is the most common propeller material for recreational boats due to its low cost, light weight, and ease of repair after minor strikes.

Question 4

What is the correct procedure for removing a stuck aluminum propeller from a splined shaft?

Accepted Answer

Use a propeller puller or soak with penetrating oil and tap gently

Answer

A propeller puller or penetrating oil with gentle tapping is the correct approach to avoid damaging the splined shaft or distorting the propeller hub.

Question 5

What does adding 'cup' to a propeller blade accomplish?

Accepted Answer

Adds a curved hook to the trailing edge to improve grip and reduce ventilation

Answer

Cup is a curved trailing edge on propeller blades that improves water grip, reduces ventilation and cavitation, and helps the engine maintain rated RPM.

(MST) Marine Service Technician Practice Test

(MST) Marine Service Technician Practice Test

MST Marine Propulsion & Propeller Systems