100-Ton Master Deck General Practice Questions

Sample questions — Deck General

Drawn from the same bank used on USCG licensing exams. Correct answers and explanations are shown — read every explanation, even for questions you get right.

1. 1. Which knot is most suitable for joining two lines of equal diameter?

   • A.Square knot✓
   • B.Sheet bend
   • C.Bowline
   • D.Clove hitch

   Why: The square knot (reef knot) is designed for joining two lines of equal size and is commonly used to tie off reefing points and bundling. It should not be used for critical load-bearing applications or lines of unequal diameter.

2. 2. A timber hitch is most commonly used to:

   • A.Moor a vessel to a dock pile
   • B.Start the securing of a spar or log for towing or hoisting✓
   • C.Attach a heaving line to a hawser
   • D.Belay a line around a cleat

   Why: The timber hitch is specifically designed to temporarily secure around a spar, log, or pipe for dragging or hoisting; it tightens under load and releases easily when the strain is removed. It is often combined with a half hitch for directional control.

3. 3. A heaving line is attached to a mooring hawser using which knot?

   • A.Bowline
   • B.Monkey's fist with a running bowline
   • C.Clove hitch
   • D.Double sheet bend✓

   Why: A double sheet bend is the standard method for bending a heaving line to a mooring hawser eye or bight; the double form is used because the great difference in diameter between the light heaving line and the heavy hawser requires the extra tuck for security.

4. 4. When a vessel is required to anchor in a designated anchorage area, what signal must it display by day per COLREGS Rule 30?

   • A.A black diamond shape in the forward part of the vessel
   • B.A black ball shape in the forward part of the vessel✓
   • C.Two black balls in a vertical line
   • D.A white light visible all around the horizon

   Why: COLREGS Rule 30 requires a vessel at anchor to display a black ball shape in the forward part of the vessel during daylight hours. This shape must be visible in all directions to warn other vessels of the anchored vessel's presence.

5. 5. When using a kedge anchor to warp a vessel in a harbor, the kedge rode is best made fast to which part of the vessel to control the direction of movement?

   • A.Always the stern bitts to pull the stern first
   • B.The appropriate bitts or winch that will achieve the desired direction of movement based on the kedge position✓
   • C.The anchor windlass only, regardless of direction
   • D.The midship cleat to keep the pull centered and prevent yawing

   Why: The kedge rode should be led to whichever fitting — bow, stern, or midship — will produce the desired direction of movement; for example, fastening to the bow and pulling draws the bow toward the kedge, while using the stern leads the stern in that direction.

6. 6. The free surface correction (loss of GM) due to a slack tank depends primarily on which factor?

   • A.The breadth of the free surface in the tank (varies as the cube of the breadth)✓
   • B.The total weight of liquid in the tank
   • C.The height of the liquid above the tank bottom
   • D.The density of seawater versus the density of the tank liquid

   Why: The free surface correction = (ρ_liquid / ρ_seawater) × (i / Δ), where i is the second moment of area of the free surface about its own longitudinal axis, which varies as the cube of the tank breadth. A wider tank has a disproportionately greater free surface effect.

7. 7. According to Load Line regulations and IMO stability criteria, the minimum required area under the GZ curve from 0° to 30° of heel for most vessels is:

   • A.0.055 metre-radians✓
   • B.0.030 metre-radians
   • C.0.090 metre-radians
   • D.0.200 metre-radians

   Why: IMO Resolution A.749(18) (Code on Intact Stability) requires that the area under the GZ curve from 0° to 30° shall not be less than 0.055 m·rad, and from 0° to 40° not less than 0.090 m·rad, as part of the minimum intact stability criteria.

8. 8. A vessel is approaching a berth with a current running parallel to the dock from ahead. What is the safest strategy?

   • A.Come alongside heading into the current to maintain steerage and control✓
   • B.Come alongside heading with the current to use its force to push against the dock
   • C.Use a stern anchor to hold position while lines are passed
   • D.Approach beam-to the current at maximum rudder

   Why: A vessel should always approach a berth heading into the current when possible. This provides maximum rudder effectiveness and allows the current to slow the approach, giving the pilot better control during the final landing.

9. 9. When a vessel is making sternway, the rudder's effect on turning direction is:

   • A.The same as when going ahead — right rudder turns the bow to starboard
   • B.Reversed — right rudder causes the bow to swing to port✓
   • C.Ineffective regardless of position because water cannot flow over the rudder astern
   • D.Dependent entirely on propeller transverse thrust, with the rudder having no effect

   Why: When making sternway, the water flow over the rudder is reversed, so the effect is opposite to going ahead. Right rudder while backing causes the bow to swing to port (and the stern to starboard). This reversal must be remembered during docking maneuvers.

10. 10. A vessel has a very small but still positive GM. This vessel is best described as:

    • A.Stiff, likely to snap-roll
    • B.Tender, with a long slow rolling period and reduced comfort margin✓
    • C.Neutrally stable with zero righting moment
    • D.In a state of loll

    Why: A small positive GM means the righting moment is weak. The vessel rolls slowly (long period) and is called tender. Although technically stable, the small margin increases the risk of a dangerous list or capsize if additional weight is added high.

11. 11. Free surface effect (FSE) is caused by:

    • A.Water on the weather deck draining to the low side
    • B.A liquid in a slack (partially filled) tank shifting when the vessel heels, creating a virtual rise of G✓
    • C.The movement of B toward the low side when the vessel heels
    • D.Air spaces trapped beneath the waterline reducing buoyancy

    Why: When a vessel heels, a free surface in a slack tank allows the liquid to flow to the low side. This shift produces a heeling moment that acts as if G has risen. The effective GM is reduced by the free surface correction: GM_eff = GM_solid - FSC.

12. 12. What condition most commonly leads to a vessel developing an angle of loll?

    • A.Loading too much ballast in the double bottom
    • B.Consuming fuel and water from low tanks during a voyage, raising G✓
    • C.Overloading the vessel beyond its summer load line
    • D.Free communication with the sea through an open sea chest

    Why: As a voyage progresses, fuel and fresh water are consumed from low tanks. This removes weight from below G, causing G to rise. If G rises above M, GM becomes negative and the vessel develops a loll. This is why stability must be monitored throughout a voyage, not just at departure.

13. 13. A line made of polypropylene has which distinctive characteristic that makes it useful for heaving lines and rescue throws?

    • A.It has the highest breaking strength of all synthetics
    • B.It floats on the water surface✓
    • C.It is completely UV-resistant
    • D.It has the greatest elasticity of all rope materials

    Why: Polypropylene is the only common rope fiber with a specific gravity less than 1.0, so it floats. This makes it ideal for heaving lines, life ring pendants, and man-overboard gear where the line must remain visible on the surface. Nylon has higher breaking strength and greater elasticity; polypropylene degrades relatively quickly in UV light.

14. 14. When anchoring in moderate weather, the recommended scope (ratio of rode length to water depth) is generally:

    • A.2:1 to 3:1
    • B.5:1 to 7:1✓
    • C.10:1 to 12:1
    • D.1:1 — the rode is equal to the depth

    Why: A scope of 5:1 to 7:1 is the standard recommendation for moderate conditions. Greater scope keeps the pull on the anchor more horizontal, maximizing holding power. In storm conditions, 10:1 may be needed. Scope must account for total depth from hawsepipe to bottom, not just chart depth.

15. 15. A fire in the engine room involving spilled diesel fuel is classified as which class?

    • A.Class A
    • B.Class B✓
    • C.Class C
    • D.Class D

    Why: Class B fires involve flammable and combustible liquids (fuels, oils, greases, paints, solvents) and flammable gases. Diesel fuel is a combustible liquid; gasoline and oil are classic Class B fuels. The primary extinguishing method is smothering or flame inhibition — NOT a water jet, which can spread burning liquid.

16. 16. A sprinkler system that holds water in the pipes at all times and opens individual heat-activated heads is called a:

    • A.Deluge system
    • B.Pre-action system
    • C.Wet pipe system✓
    • D.Dry pipe system

    Why: A wet pipe sprinkler system maintains pressurized water in the distribution piping at all times. Individual sprinkler heads have a heat-sensitive fusible element that opens when the temperature at that head reaches its rated temperature, releasing water only at the location of the fire. Deluge systems open all heads simultaneously. Dry pipe systems use pressurized air to hold a valve closed until heat activates a head.

17. 17. How many persons must a lifeboat on a cargo vessel be capable of carrying, as a minimum requirement on each side of the vessel under SOLAS?

    • A.All persons aboard
    • B.50% of total persons aboard on each side✓
    • C.25% of total persons aboard on each side
    • D.At least 6 persons

    Why: SOLAS requires cargo ships to carry lifeboats on each side capable of holding 100% of persons aboard (i.e., each side carries 50% of the total complement), ensuring everyone can board from either side in the event one side is inaccessible.

18. 18. What is the correct action when inadvertently activating a 406 MHz EPIRB that is properly registered with NOAA?

    • A.Leave it activated so responders can confirm it was accidental
    • B.Immediately deactivate it and notify the U.S. Coast Guard and NOAA to cancel the alert✓
    • C.Submerge the EPIRB in seawater to stop the signal
    • D.File a written report with the FCC within 72 hours

    Why: If a 406 MHz EPIRB is inadvertently activated, the operator must immediately deactivate it and notify the USCG (via VHF Channel 16 or phone) and NOAA to cancel the distress alert. Failure to report a false alert wastes significant SAR resources and may subject the vessel operator to civil penalties.

19. 19. A vessel loading in fresh water will float at a different draft than in salt water because:

    • A.Fresh water is denser than salt water, so the vessel floats lower
    • B.Fresh water is less dense than salt water, so the vessel sinks deeper for the same displacement✓
    • C.Fresh water has no effect on draft; only cargo weight determines draft
    • D.Salt water provides more buoyancy due to its temperature being lower

    Why: Salt water has a density of approximately 1.025 t/m3 versus 1.000 t/m3 for fresh water. Since fresh water is less dense, a vessel displaces more volume to support the same weight, causing it to sit deeper. The 'F' (Fresh) and 'TF' (Tropical Fresh) marks account for this difference.

20. 20. 33 CFR Part 164 (Navigation Safety Regulations) requires vessels over 1,600 gross tons operating in U.S. waters to have the vessel's position recorded in the log at least:

    • A.Every 15 minutes
    • B.Every hour✓
    • C.Every 4 hours
    • D.At each watch change

    Why: 33 CFR Part 164 requires that vessels over 1,600 gross tons record their position at hourly intervals when underway in U.S. waters. This navigation safety regulation ensures a continuous position record that can be used in accident investigations and helps officers maintain situational awareness.

Frequently asked questions

Is Deck General on the 100-Ton Master exam?

Yes — Deck General is one of the tested modules on the 100-Ton Master licensing exam. Candidates must score 70% on each module to pass.

How many Deck General questions are on the 100-Ton Master exam?

The USCG draws from a bank of 267 Deck General questions across all exams. The exact number on any single sitting varies, but Rules of the Road is typically the largest module and has the highest passing threshold (90%).

What is the best way to study Deck General for the 100-Ton Master exam?

Work through the practice questions in this bank until you can answer them consistently above the passing threshold. Review every explanation — understanding why the wrong answers are wrong matters more than memorizing facts.