Marine Propulsion & Propeller Systems Flashcards
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Read the first 7 Marine Propulsion & Propeller Systems flashcards as text
What is cavitation in a marine propeller?
Answer: The formation and collapse of vapor bubbles on propeller blades due to low pressure
Cavitation occurs when low pressure on the blade face causes water to vaporize, forming bubbles that collapse violently and erode the blade surface.
What does propeller pitch refer to in marine applications?
Answer: The theoretical distance a propeller would advance in one revolution with no slip
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.
Which material is most commonly used for recreational boat propellers?
Answer: Aluminum alloy
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.
What is the correct procedure for removing a stuck aluminum propeller from a splined shaft?
Answer: Use a propeller puller or soak with penetrating oil and tap gently
A propeller puller or penetrating oil with gentle tapping is the correct approach to avoid damaging the splined shaft or distorting the propeller hub.
What does adding 'cup' to a propeller blade accomplish?
Answer: Adds a curved hook to the trailing edge to improve grip and reduce ventilation
Cup is a curved trailing edge on propeller blades that improves water grip, reduces ventilation and cavitation, and helps the engine maintain rated RPM.
What is propeller slip?
Answer: The difference between theoretical speed based on pitch and actual boat speed
Propeller slip is the difference between theoretical speed (pitch × RPM) and actual boat speed, expressed as a percentage, representing inefficiency in the propeller's grip on water.
How does a 4-blade propeller generally differ from a 3-blade of the same pitch and diameter?
Answer: 4-blade provides better hole shot and reduced vibration but slightly lower top speed
A 4-blade propeller offers better acceleration and less vibration due to increased blade area, but the added drag typically results in a slightly lower maximum top speed.