MMC Upgrade Towing Practice Questions

Sample questions — Towing

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. For the purpose of the towing light rules, the 'length of the tow' is measured from the:

   • A.Stern of the towing vessel to the after end of the tow✓
   • B.Bow of the towing vessel to the bow of the first barge
   • C.Bridge of the towing vessel to the middle of the tow
   • D.Waterline to the highest point of the deck cargo

   Why: Length of tow is measured from the stern of the towing vessel to the after end of the tow. It is the trigger for the 200-meter threshold that adds a third masthead light and the diamond day shape.

2. 2. In a towing bridle, the fishplate (or flounder plate) is the fitting that:

   • A.Holds the navigation lights on the barge
   • B.Pumps water from the barge
   • C.Connects the legs of the bridle to the towing hawser✓
   • D.Marks the centerline of the deck cargo

   Why: The fishplate (flounder plate) is the triangular plate that joins the two legs of the bridle to the single towing hawser or pendant, distributing the towing load to both sides of the barge's bow.

3. 3. Subchapter M generally applies to U.S. towing vessels that are:

   • A.Only those over 1,600 gross tons
   • B.26 feet (about 7.9 meters) or more in length (with specified exceptions)✓
   • C.Only vessels operating on the high seas
   • D.Sailing vessels of any length

   Why: Subchapter M applies to towing vessels 26 feet or more in length, plus certain shorter vessels moving oil or hazardous materials, with specific exclusions (for example, some assistance-towing and recreational situations).

4. 4. Pre-employment, random, post-casualty, and reasonable-cause chemical testing of crewmembers is required under:

   • A.The vessel's TSMS only, with no federal basis
   • B.State boating regulations
   • C.The towing company's insurance policy
   • D.46 CFR Part 16 (chemical testing)✓

   Why: 46 CFR Part 16 mandates the marine chemical-testing program — pre-employment, periodic/random, post-serious-marine-incident, and reasonable-cause drug and alcohol testing — for crewmembers on U.S. commercial vessels, including towing vessels.

5. 5. When adjusting tow line scope in moderate swells, the primary goal is to ensure that:

   • A.The tow line never becomes slack under any wave condition
   • B.The towing vessel and tow are in the same phase of wave motion to minimize surge loads✓
   • C.The tow is kept as close as possible to the towing vessel to improve maneuverability
   • D.The scope equals at least twice the depth of water under the keel

   Why: Proper scope is adjusted so that both vessels rise and fall together on the same wave, keeping both in phase. If they are out of phase, one vessel rises while the other descends, causing violent snatching loads on the gear; scope is typically adjusted until the tow line has a steady, even sag.

6. 6. When determining the safe working load (SWL) of a tow line, the conventional safety factor applied to the manufacturer's minimum breaking strength (MBS) for towing operations is:

   • A.2:1 (SWL = 50% of MBS)
   • B.3:1 (SWL = 33% of MBS)✓
   • C.5:1 (SWL = 20% of MBS)
   • D.10:1 (SWL = 10% of MBS)

   Why: Industry standard for towing gear applies a minimum safety factor of 3:1 on the minimum breaking strength, yielding a safe working load of approximately one-third of MBS. This accounts for dynamic surge loads, wear, and uncertainty in actual line condition; some authorities use a 5:1 factor for critical towing operations.

7. 7. Before beginning to pay out a tow hawser from the towing vessel, what MUST be verified first?

   • A.The bitter end of the hawser is secured to the vessel with a safety line or chain stopper✓
   • B.The tow has taken in all slack on its anchor chain to prevent snagging
   • C.The hawser has been flaked on deck to prevent fouling as it runs out
   • D.The towing winch brake is set to slip at exactly the hawser's safe working load

   Why: The bitter end of any tow hawser must always be secured to the vessel before paying out. If the hawser runs out uncontrolled — due to a winch failure, brake slip, or inattention — and the bitter end is not secured, the vessel loses the tow completely. A chain stopper or safety pennant on the bitter end is a fundamental safety requirement.

8. 8. When towing alongside (hip tow) in a harbor, which type of towline material is generally preferred for the working lines?

   • A.Wire rope, for maximum strength
   • B.Polypropylene, because it floats and avoids fouling propellers
   • C.Nylon or other synthetic fiber, for shock absorption and ease of handling✓
   • D.Manila, for its traditional reliability and low stretch

   Why: Synthetic fiber lines (nylon, polyester) are preferred for hip towing because they are easier to handle, can be surged on cleats to manage loads, and their elasticity absorbs the frequent tugging and maneuvering loads. Wire rope is difficult to manage for the short, dynamic connections of hip towing.

9. 9. Which item is MOST important to confirm during pre-tow communications with the master of a vessel to be towed?

   • A.The tow vessel's insurance carrier and policy number
   • B.The tow vessel's cargo manifest and stowage plan
   • C.Structural integrity of tow fittings, bridle condition, and any known hazards aboard the tow✓
   • D.The nationality and documentation status of all crew aboard the tow

   Why: Before commencing a tow, the towing vessel master must confirm the condition and adequacy of the tow's fittings, bridle, and bitts, and be informed of any structural damage, flooding, or other hazards. Defective tow fittings are a leading cause of towline system failures.

10. 10. The breaking strength of a wire rope towing hawser is reduced by the presence of a splice. A properly made long splice in wire rope reduces breaking strength by approximately:

    • A.Less than 5% — the long splice is nearly as strong as the original wire
    • B.10-15% compared to an unspliced wire of the same size✓
    • C.30-40% compared to an unspliced wire
    • D.50% — a splice always reduces strength by half

    Why: A properly made long splice in wire rope retains approximately 85-90% of the rope's original breaking strength, reducing it by approximately 10-15%. Short splices and mechanical connections reduce strength further. This reduction must be factored into towline working load calculations.

11. 11. The distinction between a LOLL and a LIST is important in towing operations. Which statement is CORRECT?

    • A.A list results from G being off-center; a loll results from G being above M with the vessel finding a new angle of equilibrium at a positive righting lever✓
    • B.A loll results from G being off-center; a list results from negative GM
    • C.Both list and loll result from negative GM but at different angles of heel
    • D.List and loll are interchangeable terms describing the same stability condition

    Why: A list is caused by G being off the centerline (transverse shift of weight), while a loll occurs when GM is negative — G is above M — and the vessel heels until it finds a new angle where the righting lever is positive. Corrective action differs: ballasting the high side corrects a list but can capsize a vessel in loll.

12. 12. An inland towing vessel is pushing a loaded hopper barge. The barge's cargo shifts transversely during a turn. Which combination of effects is MOST dangerous to the overall tow unit's stability?

    • A.Cargo shift raises barge G and creates a transverse moment, while the turning heel moment acts in the same direction✓
    • B.Cargo shift lowers the barge's G, increasing GM beyond the structural limit of the rake
    • C.The turning moment acts opposite to the cargo shift, partially self-correcting the heel
    • D.A transverse cargo shift in a pushed barge does not affect the pushing tug's stability

    Why: When a transverse cargo shift and a dynamic heeling moment (from turning) act in the same direction, the combined heeling moment can exceed the righting moment at a given angle, potentially causing capsize. This additive effect is a critical consideration in tow stability planning.

13. 13. A tow barge is upright and stable at the start of a voyage. After 12 hours at sea, the barge has developed a 7° starboard list. The barge master reports no cargo shift and all deck fittings appear secure. The towing vessel master's MOST prudent action is to:

    • A.Divert to the nearest port or sheltered anchorage, inspect for flooding, and correct the list before continuing the voyage✓
    • B.Continue the voyage at reduced speed and monitor the list hourly, reporting to the owner
    • C.Deploy additional ballast by overboard-pumping fresh water from the port side tanks
    • D.Request a USCG inspection at the next scheduled port and document the list in the log

    Why: An unexplained 7-degree list developing over 12 hours, with cargo shift and deck fittings ruled out, most likely indicates progressive flooding, which can lead to loss of the tow; the prudent mariner's duty of care requires diverting to inspect and correct the list before continuing. Such flooding affecting the barge's seaworthiness is also a reportable marine casualty under 46 CFR 4.05-1 and a hazardous condition requiring immediate Coast Guard notice under 33 CFR 160.216.

14. 14. Under the TPO compliance option of Subchapter M, a towing vessel owner must implement which type of management system?

    • A.An International Safety Management (ISM) Code-compliant system
    • B.A USCG-accepted Safety Management System (SMS)✓
    • C.An ISO 9001-certified quality management system
    • D.A vessel response plan approved by the National Response Center

    Why: The TPO compliance pathway under 46 CFR Subchapter M requires the vessel owner to develop and implement a Safety Management System (SMS) accepted by the Coast Guard, covering safety and environmental protection policies, procedures, and responsibilities per 46 CFR Part 138.

15. 15. Under 46 CFR Subchapter M (Part 141), each person on a towing vessel operating on inland waters must have access to which minimum lifesaving equipment?

    • A.An inflatable life raft with a capacity equal to the total number aboard
    • B.An approved life preserver (Type I PFD) or equivalent✓
    • C.A dry suit rated for the operating water temperature
    • D.A personal EPIRB registered to the vessel

    Why: 46 CFR 141.305 requires that each person aboard a towing vessel have access to a USCG-approved personal flotation device (Type I PFD or equivalent). Inland vessels have fewer lifesaving appliance requirements than ocean-going vessels but must still meet minimum PFD standards.

16. 16. A partially filled (slack) tank aboard a towing vessel reduces the vessel's stability because of free-surface effect. This effect causes:

    • A.A permanent increase in displacement
    • B.A virtual rise in the vessel's center of gravity, reducing GM and the righting arm✓
    • C.An increase in metacentric height (GM)
    • D.A lowering of the center of buoyancy

    Why: Liquid shifting in a slack tank moves the center of gravity toward the low side, producing a virtual rise in G that reduces effective GM and the righting arm. Free surface never increases GM; pressing tanks up or down minimizes it.

17. 17. Why is a shackle pin in a towing connection 'moused' (seized) with wire?

    • A.To increase the shackle's safe working load
    • B.To prevent the pin from backing out and unscrewing under vibration and cyclic loading✓
    • C.To make the pin easier to remove quickly in an emergency
    • D.To electrically bond the shackle to the towed vessel

    Why: Mousing seizes the threaded pin so working loads, vibration, and motion cannot unscrew it, which would otherwise let the connection part. It does not change the rated strength and actually makes the pin slower (not easier) to remove.

18. 18. If the tug and tow begin surging on a following or quartering sea so that the towline repeatedly goes slack and snaps taut, the towing master should FIRST:

    • A.Increase speed sharply to take and hold a steady strain
    • B.Adjust speed and/or towline length to change the timing and break up the surging✓
    • C.Cast off the tow until the seas moderate
    • D.Heave the towline as short as possible

    Why: Changing speed and/or scope alters the relationship between the tug's and tow's motion in the seas, breaking up the surging cycle that causes the line to alternately slack and snap taut. A sharp speed increase or very short scope can actually worsen peak tension, and casting off is not a routine first response.

19. 19. An inconspicuous, partly submerged object being towed, where the length of the tow exceeds 200 meters, shall display by day:

    • A.A single black ball
    • B.A diamond shape at or near the aftermost extremity of the tow✓
    • C.Two cones apex together
    • D.Two black balls in a vertical line

    Why: Rule 24(g)(iv) requires a diamond shape at or near the aftermost extremity of an inconspicuous partly submerged tow when the tow length exceeds 200 m. The diamond marks the excess-length condition, consistent with the general 200 m rule.

20. 20. By day, when the length of a tow (from the stern of the towing vessel to the after end of the tow) exceeds 200 meters, what shape must be exhibited where it can best be seen?

    • A.A black ball
    • B.A diamond shape on both the towing and towed vessels✓
    • C.A cone, apex downward
    • D.Two diamond shapes in a vertical line

    Why: COLREGS Rule 24(a)(v) requires that when the length of the tow exceeds 200 meters, a diamond shape be exhibited where it can best be seen on the towing vessel, and Rule 24(e)(iv) requires the towed vessel(s) to exhibit a diamond shape where it can best be seen when the tow exceeds 200 meters. This is in addition to the towing lights at night.

Frequently asked questions

Is Towing on the MMC Upgrade exam?

Yes — Towing is one of the tested modules on the MMC Upgrade licensing exam. Candidates must score 70% on each module to pass.

How many Towing questions are on the MMC Upgrade exam?

The USCG draws from a bank of 210 Towing 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 Towing for the MMC Upgrade 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.