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These 10 free USCG-M500-1600 questions are organized by exam domain, so you can see how each part of the National Master 500/1600 OC or NC (USCG-M500-1600) blueprint is tested. Reveal the answer and explanation under each question.
In daylight, a dredge working in a channel displays a ball-diamond-ball vertically. Two additional balls are displayed on its starboard side and two diamonds on its port side. Your approach is from ahead of the dredge. What do the additional shapes indicate?
Correct answer: A - The dredge's port side is marked as the side available for passage.
In clear visibility outside any narrow channel or traffic separation scheme, two power-driven vessels are crossing. The other vessel is on your port side and has made an early, substantial alteration to pass well astern. Continued observation confirms a safe passing distance, with no other developing hazard. How should you handle your vessel during the crossing?
Correct answer: A - Maintain course and speed while monitoring the other vessel's maneuver.
While making headway close to a steep starboard channel bank, a twin-screw vessel begins to sheer to port and its stern closes the bank. The engines remain at equal ahead settings, the rudder answers correctly, and there is no appreciable wind. Which explanation best fits both movements?
Correct answer: D - Bank cushion at the bow and bank suction at the stern.
During discharge, a damaged package marked Division 4.3 DANGEROUS WHEN WET leaks powder onto the deck. A deckhand proposes washing the powder into a collection tray. Which characteristic of this division makes that proposal unsafe?
Correct answer: B - Possible release of flammable gas on contact with water.
An engine-room fire continues to spread after the attack team withdraws. Everyone is accounted for outside the space; fuel supplies are isolated, ventilation is stopped, and the required openings are closed. The fixed CO₂ system is ready, and its pre-discharge procedure is complete. What should the master do next?
Correct answer: D - Discharge the fixed CO₂ system and maintain the space sealed.
During inspection of a float-free inflatable liferaft, a mate proposes replacing the manufacturer's painter weak link with stronger line so the raft cannot break away. In a correctly rigged installation, what essential function would this defeat?
Correct answer: A - Allowing the inflated raft to separate from the sinking vessel.
A loading review gives displacement 2,000 metric tonnes, KM 5.60 m, and uncorrected KG 4.40 m. A 100-tonne load already aboard is moved vertically from a center of gravity 2.0 m above the keel to 8.0 m above it. Displacement and KM remain unchanged. The final total free-surface moment is 400 tonne-metres. The vessel's approved minimum free-surface-corrected GM for this condition is 0.80 m. Select the correct final GM and assessment of this requirement.
Correct answer: B - 0.70 m; below the approved minimum.
Southbound on the Atlantic Intracoastal Waterway, you reach a crossing with an inlet channel. A green can buoy carries a yellow triangle. Your intended track continues along the Intracoastal Waterway. Which interpretation of the marking applies to your passage?
Correct answer: C - Follow the yellow triangle and leave the buoy to starboard.
Plot a simultaneous two-bearing fix from these charted positions: West Light, 34°56.0′N 076°24.0′W; East Light, 34°56.0′N 076°18.0′W. The observed true bearings from the vessel are West Light 315°T and East Light 045°T. For this small-area plot, use 0.82 nautical mile per minute of longitude and 1 nautical mile per minute of latitude. Where is the vessel, approximately?
Correct answer: D - 34°53.5′N 076°21.0′W.
The next coastal leg must make good 090°T. Speed through the water will be 12.0 knots, and a steady current sets 180°T at 3.0 knots. There is no leeway. Which course to steer and resulting speed over ground belong in the passage calculation?
Correct answer: C - 075.5°T and 11.6 knots.
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