MST Boat Systems & Maintenance 3 — Questions and Answers
Question 1: A bilge pump rated at 1,500 GPH at zero head will deliver how much flow at 1 meter of head?
- Approximately 1,500 GPH — head does not affect output
- Significantly less than 1,500 GPH due to increased resistance (Correct answer)
- More than 1,500 GPH because pressure assists flow
- Exactly 750 GPH regardless of pump type
Correct answer: Significantly less than 1,500 GPH due to increased resistance
Pump output decreases as lift height (head) increases; rated GPH at zero head always overstates real-world performance.
Question 2: What is the function of a sacrificial zinc anode on a boat's underwater gear?
- Lubricate the propeller shaft seal
- Provide cathodic protection by corroding in place of more noble metals (Correct answer)
- Reduce propeller cavitation
- Balance the boat's trim
Correct answer: Provide cathodic protection by corroding in place of more noble metals
Zinc is less noble than bronze or stainless steel, so it corrodes preferentially, protecting underwater metal components from galvanic corrosion.
Question 3: When inspecting a through-hull fitting, a technician finds the seacock is stiff and difficult to operate. What is the correct action?
- Apply marine grease and exercise the seacock; replace if operation does not improve (Correct answer)
- Leave it in place because stiff seacocks are less likely to open accidentally
- Wrap the handle with duct tape to prevent unintended movement
- Replace only the handle assembly
Correct answer: Apply marine grease and exercise the seacock; replace if operation does not improve
Seacocks must operate freely for emergency use; they should be greased and exercised regularly, and replaced if they remain stiff or corroded.
Question 4: Which instrument reading most directly indicates engine cylinder pressure balance on a multi-cylinder marine engine?
- Coolant temperature gauge
- Compression test results across all cylinders (Correct answer)
- Oil pressure reading at idle
- Exhaust gas temperature at the manifold
Correct answer: Compression test results across all cylinders
Compression testing each cylinder and comparing the results directly measures combustion chamber integrity and piston ring sealing.
Question 5: On a marine VHF radio installation, what is the maximum allowed voltage drop for the DC supply circuit under load?
- 3 volts
- 1 volt (Correct answer)
- 0.5 volt
- 5 volts
Correct answer: 1 volt
ABYC E-11 specifies a maximum 1-volt drop for electronics circuits to ensure reliable equipment operation at rated specifications.
Question 6: A technician is winterizing a raw-water cooled outboard. What is the last step before storage?
- Change the gear lube
- Fog the cylinders with storage oil after flushing with antifreeze or blowing out water passages (Correct answer)
- Disconnect the battery
- Polish the lower unit
Correct answer: Fog the cylinders with storage oil after flushing with antifreeze or blowing out water passages
Cylinder fogging with storage oil coats internal surfaces to prevent corrosion during the off-season after water has been expelled from the cooling system.
Question 7: What condition is indicated when a two-stroke outboard consistently runs rich at wide-open throttle but lean at idle?
- Clogged high-speed main jet
- Faulty carburetor needle clip position or worn needle jet (Correct answer)
- Failed ignition timing advance
- Air leak at the intake manifold
Correct answer: Faulty carburetor needle clip position or worn needle jet
The needle and needle jet control the mid-range and transition to wide-open throttle; a worn or mispositioned needle causes rich WOT and lean idle symptoms.
MST Boat Systems & Maintenance 3
A bilge pump rated at 1,500 GPH at zero head will deliver how much flow at 1 meter of head?