Vessel Documentation and Numbering: Display Requirements and Hull Markings

TL;DR — A vessel number displayed under a conditional permit must appear in block figures at least 18 inches high, on a contrasting background, and be readily visible from either side of the vessel; no person may tamper with or falsify that number. 33 CFR §151.1024

---

What the Rule Says

Conditional Permit Number Display

Under 33 CFR §151.1024, the owner or operator of each vessel subject to that subpart must ensure the vessel number stated on the conditional permit issued under §151.1015 is displayed so that it meets all four of the following criteria: 33 CFR §151.1024

1. Clearly legible — the number must be readable without ambiguity. 33 CFR §151.1024 2. Contrasting background — the figures must stand out from the surface on which they are painted or affixed. 33 CFR §151.1024 3. Readily visible from either side of the vessel — bilateral visibility is mandatory; displaying the number only on one side does not satisfy the requirement. 33 CFR §151.1024 4. Block figures at least 18 inches in height — this is the minimum character height; no exceptions for smaller vessels are stated in this section. 33 CFR §151.1024

Additionally, no person may tamper with or falsify a number required under this section. This prohibition applies to any person, not merely the owner or operator. 33 CFR §151.1024

Hull Markings for Passenger Vessels

Under 46 CFR §185.602, each vessel subject to that subpart must be marked as required by 46 CFR part 67, subpart I. Beyond that general requirement, vessels that do not demonstrate compliance under §178.310(c) must carry one of two types of permanent marks: 46 CFR §185.602

Permanent draft marks at each end of the vessel, or 46 CFR §185.602
Permanent loading marks placed on each side of the vessel forward and aft to indicate maximum allowable trim, and amidships to indicate maximum allowable draft. 46 CFR §185.602

A loading mark required under this section must be a horizontal line of at least 205 millimeters (8 inches) in length and 25 millimeters (1 inch) in height, with its upper edge passing through the point of maximum draft, painted in a contrasting color to the sideshell paint. 46 CFR §185.602

Where a vessel has a load line, the amidships marks must be those required by the International Convention on Load Lines, 1966. 46 CFR §185.602

Where draft marks are obscured by operational constraints or protrusions, the vessel must be fitted with a reliable draft indicating system from which bow and stern drafts can be determined. 46 CFR §185.602

Where the number of passengers permitted on upper decks is limited by stability criteria as indicated by the vessel's stability letter, the maximum number of passengers allowed on an upper deck must be indicated by a durable marking of at least 25 millimeters (1 inch) numbers and letters at the entranceway to that deck. 46 CFR §185.602

Master's Continuing Responsibility

Regardless of any numbering or marking compliance, nothing in the applicable subpart relieves the master of responsibility for ensuring the safety and stability of the vessel or the safety of the crew and passengers, or any other responsibility. 33 CFR §151.1514

Commercial Fishing Vessel Applicability

Part 46 CFR Part 28 applies to all United States flag vessels not inspected under that chapter that are commercial fishing, fish processing, or fish tender vessels. This includes both documented vessels (those holding a Certificate of Documentation under 46 CFR part 67) and vessels numbered by a State or the Coast Guard under 33 CFR subchapter S. The regulations in Part 28 have preemptive effect over State or local regulations in the same field. 46 CFR §28.30

Under 46 CFR §28.50, the term "length" as used in Part 28 means the length listed on the vessel's Certificate of Documentation or Certificate of Number. 46 CFR §28.50

A documented vessel, as defined in Part 28, means a vessel for which a Certificate of Documentation has been issued under the provisions of 46 CFR part 67. 46 CFR §28.50

Under 46 CFR §25.10-2, navigation lights are those lights prescribed by the Navigation Rules to indicate a vessel's presence, type, operation, and relative heading. 46 CFR §25.10-2

---

Why It Matters on the Exam

OUPV and Master 100 GT written examinations regularly test candidates on the specific dimensional and display requirements for vessel identification numbers. The examiners favor questions that require you to recall exact measurements rather than general concepts. The following points are the most frequently tested:

The 18-inch minimum. Exam distractors commonly offer 12 inches, 24 inches, or "at least 3 inches" as alternatives. The correct answer is block figures at least 18 inches in height. 33 CFR §151.1024

Bilateral visibility. The number must be readily visible from either side of the vessel. A single-side display does not comply. Exam questions may describe a scenario where the number is painted only on the port side and ask whether the vessel is in compliance — it is not. 33 CFR §151.1024

Contrasting background. The requirement is not merely that the number be painted on the hull; the background must contrast with the figures. This is a separate, independently testable requirement. 33 CFR §151.1024

Tampering prohibition. The prohibition on tampering or falsifying the number applies to any person, not just the owner or operator. This distinction can appear in questions framed around crew members or third parties. 33 CFR §151.1024

Hull marking dimensions for passenger vessels. The loading mark horizontal line must be at least 205 mm (8 inches) long and 25 mm (1 inch) high, with its upper edge at the point of maximum draft, in a contrasting color. 46 CFR §185.602 Exam questions may present the dimensions in metric or imperial and ask which measurement applies to which dimension.

Upper deck passenger limit markings. Where stability criteria limit passengers on upper decks, the marking at the entranceway must use numbers and letters at least 25 mm (1 inch) in height. 46 CFR §185.602

Master's responsibility is non-delegable. Compliance with documentation and numbering requirements does not transfer or diminish the master's responsibility for vessel safety and stability. 33 CFR §151.1514

Documented vs. numbered vessels in commercial fishing. Part 28 applies to both documented vessels and State- or Coast Guard-numbered vessels engaged in commercial fishing, fish processing, or fish tendering. 46 CFR §28.30 The definition of "length" for Part 28 purposes comes from the Certificate of Documentation or Certificate of Number. 46 CFR §28.50

---

Common Pitfalls

Confusing the number height with other marking dimensions. Candidates frequently mix up the 18-inch block figure requirement for conditional permit numbers 33 CFR §151.1024 with the 25 mm (1 inch) marking requirement for upper deck passenger limits 46 CFR §185.602 or the 8-inch loading mark length 46 CFR §185.602. Keep these in separate mental categories: identification numbers versus stability/loading marks.

Assuming the owner bears sole responsibility for tampering. The regulation states "no person may tamper with or falsify" the number — the prohibition is universal, not limited to the owner or operator. 33 CFR §151.1024

Overlooking the bilateral visibility requirement. Candidates sometimes focus on legibility and contrasting background while forgetting that visibility from either side is an independent, mandatory element. 33 CFR §151.1024

Assuming Part 28 applies only to documented vessels. Part 28 explicitly covers both documented vessels and numbered vessels in commercial fishing industry service. 46 CFR §28.30

Misidentifying what "length" means under Part 28. Length is not measured by the examiner or estimated; it is the length listed on the Certificate of Documentation or Certificate of Number. 46 CFR §28.50

Believing compliance with marking rules satisfies the master's safety obligations. Marking and numbering compliance is administrative. The master's duty to ensure vessel safety and stability is independent and continuous. 33 CFR §151.1514

---

Quick Check

Q1 — What is the minimum height of block figures for a vessel number displayed under a conditional permit?

At least 18 inches. 33 CFR §151.1024

Q2 — From which side(s) of the vessel must the conditional permit number be readily visible?

From either side of the vessel — bilateral visibility is required. 33 CFR §151.1024

Q3 — Who is prohibited from tampering with or falsifying a vessel number required under 33 CFR §151.1024?

No person — the prohibition applies to any person, not only the owner or operator. 33 CFR §151.1024

Q4 — What are the two options for permanent marks a passenger vessel must carry under 46 CFR §185.602 if it does not demonstrate compliance under §178.310(c)?

Either permanent draft marks at each end of the vessel, or permanent loading marks placed on each side forward and aft (for trim) and amidships (for maximum draft). 46 CFR §185.602

Q5 — What are the minimum dimensions of a loading mark required under 46 CFR §185.602?

A horizontal line at least 205 mm (8 inches) in length and 25 mm (1 inch) in height, with its upper edge at the point of maximum draft, painted in a contrasting color to the sideshell paint. 46 CFR §185.602

Q6 — Does compliance with vessel numbering and documentation requirements relieve the master of responsibility for vessel safety?

No. Nothing in the applicable subpart relieves the master of responsibility for ensuring the safety and stability of the vessel or the safety of the crew and passengers. 33 CFR §151.1514

Q7 — Under Part 28, does "length" refer to a measured or estimated dimension?

Neither. Length means the length listed on the vessel's Certificate of Documentation or Certificate of Number. 46 CFR §28.50

Q8 — Does 46 CFR Part 28 apply to a commercial fishing vessel that is numbered by a State rather than documented?

Yes. Part 28 applies to all U.S. flag uninspected commercial fishing, fish processing, and fish tender vessels, including those numbered by a State or the Coast Guard under 33 CFR subchapter S. 46 CFR §28.30