MTC MTC Steering & Propulsion Systems 1 — Questions and Answers
Question 1: What is the most common cause of excessive play (looseness) in a mechanical boat steering system?
- Incorrect propeller pitch
- Worn or stretched steering cable or loose helm connections (Correct answer)
- Misaligned rudder post
- Overfilled hydraulic reservoir
Correct answer: Worn or stretched steering cable or loose helm connections
Steering cables stretch and wear over time, and loose connections at the helm or tiller arm create play that reduces steering precision and control.
Question 2: When bleeding a hydraulic steering system on a marine vessel, what is the correct procedure?
- Add fluid and turn the wheel rapidly back and forth until bubbles stop
- Attach a vacuum pump to the fill port while turning the wheel lock-to-lock (Correct answer)
- Remove the cylinder and flush with fresh water
- Run the engine at full throttle while filling the reservoir
Correct answer: Attach a vacuum pump to the fill port while turning the wheel lock-to-lock
Using a vacuum pump at the fill port while cycling the steering wheel lock-to-lock draws air bubbles out of the system and allows clean fluid to fill all passages.
Question 3: What does 'propeller cavitation' mean in the context of marine propulsion?
- Propeller blades bending under load
- Formation and collapse of vapor bubbles on propeller blades causing pitting and loss of thrust (Correct answer)
- Propeller shaft vibration at high RPM
- Excessive propeller pitch for the engine's power output
Correct answer: Formation and collapse of vapor bubbles on propeller blades causing pitting and loss of thrust
Cavitation occurs when low pressure on the propeller blade face causes water to vaporize; when these bubbles collapse, they create micro-jets that erode the blade surface and reduce efficiency.
Question 4: What is the purpose of a trim tab on an outboard motor or sterndrive?
- To adjust engine idle speed electronically
- To control the running angle of the vessel to optimize performance and fuel efficiency (Correct answer)
- To prevent the propeller from over-spinning
- To limit maximum throttle travel
Correct answer: To control the running angle of the vessel to optimize performance and fuel efficiency
Trim tabs (on the cavitation plate or transom) adjust the bow-up or bow-down attitude of the vessel, allowing the hull to run at its most efficient planing angle.
Question 5: When inspecting a propeller shaft for runout, what tool does a marine technician use?
- Torque wrench
- Dial indicator (dial gauge) (Correct answer)
- Feeler gauge
- Micrometer only
Correct answer: Dial indicator (dial gauge)
A dial indicator measures the total indicator runout (TIR) of the shaft as it is rotated, revealing bends or eccentricity that would cause vibration and bearing wear.
Question 6: What is the function of a cutlass bearing in a marine propulsion system?
- To transfer thrust from the propeller to the hull
- To support the propeller shaft and allow it to rotate smoothly (Correct answer)
- To seal the shaft log against water intrusion
- To absorb shock loads from propeller impact
Correct answer: To support the propeller shaft and allow it to rotate smoothly
The cutlass bearing is a water-lubricated rubber bearing that supports the propeller shaft inside the strut or shaft log, reducing vibration and preventing metal-to-metal contact.
MTC MTC Steering & Propulsion Systems 1
What is the most common cause of excessive play (looseness) in a mechanical boat steering system?