Practice Test Geeks(MST) Marine Service Technician Practice Test
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Electrical Systems & Troubleshooting Flashcards

7 cards from real MST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Electrical Systems & Troubleshooting flashcards as text

  1. What does the term 'stray current corrosion' refer to in a marine context?

    Answer: Accelerated corrosion caused by DC electrical current leaking into the water from the vessel or marina

    Stray current corrosion is caused by DC current leaking from the vessel or marina electrical systems into the water, which dramatically accelerates metal corrosion on underwater components.

  2. When testing a marine DC circuit for a short to ground, a technician disconnects the load and measures resistance between the positive conductor and ground. A reading of 0 ohms confirms:

    Answer: A hard short circuit exists in the wiring between the fuse and load

    Zero ohms between the positive conductor and ground with the load disconnected confirms a hard short in the wiring, meaning the positive conductor is touching the ground somewhere.

  3. What ABYC color code designates the DC negative conductor in a 12V marine electrical system?

    Answer: Black or yellow with black stripe

    ABYC E-11 specifies black or yellow with a black stripe for DC negative conductors in marine electrical systems.

  4. A marine technician installs a new electronic chart plotter. After installation, the compass shows significant deviation only when the plotter is powered on. What is the MOST likely cause?

    Answer: Electromagnetic interference from the plotter's wiring or power supply affecting the magnetic compass

    Electronic devices and their wiring can generate magnetic fields that deviate a nearby magnetic compass; routing wiring away from the compass and using twisted pair conductors reduces this effect.

  5. On a marine vessel, what is the MAXIMUM distance the main DC overcurrent protection (fuse or circuit breaker) should be located from the battery positive terminal per ABYC standards?

    Answer: 7 inches (18 cm)

    ABYC E-11 requires the main overcurrent protection to be installed within 7 inches (18 cm) of the battery positive terminal to protect the unguarded conductor from the battery to the fuse.

  6. A technician is troubleshooting a marine vessel where the battery slowly discharges overnight with no loads switched on. The FIRST step to identify the source of the parasitic draw is to:

    Answer: Connect an ammeter in series with the battery negative cable and systematically pull fuses until the current drops

    Placing an ammeter in series on the battery negative and pulling fuses one at a time isolates which circuit is responsible for the parasitic current drain.

  7. What is the recommended minimum bend radius for marine electrical cable to prevent insulation damage?

    Answer: Three times the cable outside diameter

    ABYC standards recommend a minimum bend radius of three times the cable's outside diameter to prevent cracking or damage to the insulation.