MTC Preventive Maintenance Procedures 2 — Questions and Answers
Question 1: How often should raw water impellers on marine engines typically be inspected or replaced?
- Every 5 years regardless of use
- Every 200–300 hours or annually, whichever comes first (Correct answer)
- Only when overheating is observed
- Every 1,000 hours
Correct answer: Every 200–300 hours or annually, whichever comes first
Raw water impellers degrade with use and age, so OEM guidelines commonly specify inspection or replacement every 200–300 hours or once per season.
Question 2: What is the primary purpose of zincs (sacrificial anodes) in marine preventive maintenance?
- To improve fuel efficiency
- To protect metal components from galvanic corrosion (Correct answer)
- To lubricate the propeller shaft
- To reduce engine vibration
Correct answer: To protect metal components from galvanic corrosion
Sacrificial anodes corrode preferentially to protect more valuable metal parts from galvanic corrosion in an electrolytic environment.
Question 3: When inspecting a marine diesel fuel system during PM, which condition in the fuel filter bowl is most concerning?
- Slightly amber-colored fuel
- Clear fuel with a faint diesel odor
- Dark fuel with visible water or microbial growth (Correct answer)
- Fuel with small air bubbles
Correct answer: Dark fuel with visible water or microbial growth
Dark fuel with water or microbial (algae/bacteria) contamination can clog injectors and cause injection system damage if not addressed.
Question 4: A technician is performing PM on a marine outboard. What does checking the gear lube for a milky appearance indicate?
- The lubricant is new and unused
- Water has infiltrated the lower unit, likely via a failed seal (Correct answer)
- The gear ratio is incorrect
- The lubricant has exceeded its viscosity rating
Correct answer: Water has infiltrated the lower unit, likely via a failed seal
Milky or grey gear lube indicates water intrusion through a damaged propeller shaft seal or drain/fill plug gasket.
Question 5: During a vessel's annual PM, what is the correct procedure when replacing a stuffing box packing?
- Pack tightly until no drips occur underway
- Allow 1–2 drops per minute while underway to lubricate the shaft (Correct answer)
- Seal completely and pressure-test to 50 psi
- Replace only if visible smoke is present
Correct answer: Allow 1–2 drops per minute while underway to lubricate the shaft
A properly adjusted stuffing box should allow a slow drip (1–2 drops per minute) underway to provide lubrication and prevent overheating of the packing material.
Question 6: What is the recommended action when PM inspection reveals hairline cracks in a fiberglass hull above the waterline?
- No action needed; gelcoat cracks are purely cosmetic
- Monitor for six months before deciding on repair
- Assess depth and structural involvement, then repair to prevent moisture intrusion (Correct answer)
- Immediately haul the vessel and condemn the hull
Correct answer: Assess depth and structural involvement, then repair to prevent moisture intrusion
Hairline gelcoat cracks can allow water absorption leading to osmotic blistering or structural delamination, so they should be assessed and repaired promptly.
Question 7: Which maintenance interval item is MOST critical for a marine gasoline inboard engine to prevent carbon monoxide accumulation in the bilge?
- Changing the oil filter
- Inspecting and maintaining exhaust system integrity (Correct answer)
- Lubricating the throttle cable
- Checking the bilge pump float switch
Correct answer: Inspecting and maintaining exhaust system integrity
A leaking or deteriorated exhaust system can allow CO to enter the bilge or cabin, creating a life-threatening hazard aboard the vessel.
MTC Preventive Maintenance Procedures 2
How often should raw water impellers on marine engines typically be inspected or replaced?