Load Lines and Tonnage Basics

TL;DR — A T-boat (Subchapter T vessel) of 24 meters (79 feet) or more whose keel was laid on or after July 21, 1968, is subject to load line requirements whenever it operates on a voyage other than a domestic voyage; and an applicant for an unlimited-tonnage master or mate endorsement must obtain at least half of all required sea service on vessels of 1,600 GRT or more.

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What the Rule Says

Load Line Applicability — Subchapter T Vessels

Under 46 CFR §175.122, a vessel of 24 meters (79 feet) in length or more, the keel of which was laid or that was at a similar stage of construction on or after July 21, 1968, and that is on a voyage other than a domestic voyage is subject to load line assignment, certification, and marking under Subchapter E (Load Lines) of Title 46. Two conditions must both be satisfied before the requirement attaches: the length threshold and the non-domestic voyage. A vessel operating exclusively on domestic voyages is not triggered by this section regardless of length.

Load Line Exemption — Aleutian Fish Tender Vessels

46 CFR §28.895 carves out a narrow historical exemption for fish tender vessels of not more than 500 gross tons engaged in the Aleutian trade on non-foreign voyages. To qualify, the vessel must have operated in that trade before September 8, 1990 (or been purchased for that trade before that date and entered service before June 1, 1992), must not have undergone a major conversion, and must not have had a load line assigned at any time before November 16, 1990. Critically, 46 CFR §28.895 states that this exemption expired on January 1, 2003. Candidates should know the exemption exists historically but is no longer operative.

Master's Pre-Departure Stability and Load Line Obligation

46 CFR §185.315 places an affirmative duty on the master — not the owner, not the OCMI — to verify compliance with all applicable stability requirements after loading and prior to departure, and at all other times necessary to assure the vessel's safety. The master must consult the vessel's trim and stability book, stability letter, Certificate of Inspection, and Load Line Certificate as applicable. The vessel may not depart until it is in compliance. In fulfilling this duty, the master must account for the total weight of passengers, crew, and variable loads 46 CFR §185.315.

Total Persons Permitted — OCMI Determination

46 CFR §176.112 establishes that the cognizant OCMI determines the total number of persons permitted on a vessel. In making that determination, the OCMI may consider: total weight of passengers, crew, and variable loads; stability restrictions and subdivision requirements; the vessel's route, general arrangement, means of escape, and lifesaving equipment; minimum manning requirements; and the maximum number of passengers permitted under §176.113. The master's obligation under §185.315 and the OCMI's determination under §176.112 are complementary — the OCMI sets the ceiling, the master verifies compliance before each departure.

Tonnage Requirements — National Ocean / Near-Coastal Endorsements

46 CFR §11.402 governs tonnage thresholds for national ocean or near-coastal master and mate endorsements. To qualify for an unlimited tonnage endorsement:

1. All required experience must be obtained on vessels of 100 GRT or more 46 CFR §11.402(a)(1). 2. At least one-half of required experience must be obtained on vessels of 1,600 GRT or more 46 CFR §11.402(a)(2).

If an applicant lacks the 1,600 GRT service, a tonnage limitation is placed on the MMC. The limitation is calculated as the higher of: (a) the maximum tonnage on which at least 25 percent of required experience was obtained, or (b) 150 percent of the maximum tonnage on which at least 50 percent of service was obtained. The minimum tonnage limitation under this formula is 2,000 GRT. Limitations are expressed in multiples of 1,000 GRT, rounding up to the next higher figure. When the calculated limitation equals or exceeds 10,000 GRT, the applicant receives an unlimited tonnage endorsement 46 CFR §11.402(b).

Tonnage limitations can be removed by:

• 6 months of service on vessels of 1,600 GRT or more in the highest grade endorsed — removes all limitations 46 CFR §11.402(c)(1).
• 6 months of service on vessels of 1,600 GRT or more in any officer capacity other than the highest grade — removes limitations for that grade and raises the next higher grade to the tonnage of the vessel on which the majority of service was performed 46 CFR §11.402(c)(2).
• 12 months of service as able seaman on vessels of 1,600 GRT or more while holding a third mate endorsement — removes all tonnage limitations on the third mate endorsement 46 CFR §11.402(c)(3).

Importantly, an applicant holding a national endorsement as master or mate of vessels of less than 1,600 GRT, less than 500 GRT, or less than 25–200 GRT may not use the provisions of §11.402(c) to increase the tonnages of that endorsement 46 CFR §11.402(d).

Tonnage Requirements — Great Lakes and Inland Endorsements

46 CFR §11.431 mirrors the national ocean requirements for Great Lakes and inland unlimited endorsements: all required experience must be on vessels of 100 GRT or more, and at least one-half must be on vessels of 1,600 GRT or more. Tonnage limitations are imposed and removed in accordance with §11.402(b) and (c) 46 CFR §11.431.

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Why It Matters on the Exam

OUPV and Master 100 GT written exams test load line and tonnage rules in several predictable ways:

Load line trigger questions typically present a vessel's length and voyage type and ask whether load line assignment is required. The two-part test from 46 CFR §175.122 — 24 meters / 79 feet AND non-domestic voyage — is the answer key. Candidates who memorize only the length threshold will miss questions where the voyage is domestic.

Pre-departure stability questions ask who is responsible and what documents must be consulted. The answer is always the master, consulting the trim and stability book, stability letter, Certificate of Inspection, and Load Line Certificate, per 46 CFR §185.315. The vessel may not depart until compliance is verified.

Persons-on-board questions ask who sets the limit. That is the OCMI, per 46 CFR §176.112. The master verifies compliance; the OCMI establishes the number.

Tonnage endorsement questions test the 100 GRT / 1,600 GRT thresholds, the minimum 2,000 GRT limitation floor, the 10,000 GRT unlimited threshold, and the specific service periods required to lift limitations. These numbers appear directly on the exam 46 CFR §11.402.

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Common Pitfalls

Confusing the load line length threshold units. The regulation states 24 meters (79 feet) 46 CFR §175.122. Exam distractors may present the length in only one unit. Know both.

Forgetting the voyage-type condition. A vessel 24 meters or longer is only subject to §175.122 load line requirements on a voyage other than a domestic voyage 46 CFR §175.122. Domestic voyages are not covered by this section.

Misidentifying who sets the persons-on-board limit. The OCMI sets it 46 CFR §176.112. The master verifies compliance before departure 46 CFR §185.315. These are two different actors with two different functions.

Conflating the 100 GRT and 1,600 GRT thresholds. All experience must be on 100 GRT or more vessels; only half must be on 1,600 GRT or more vessels 46 CFR §11.402(a). Swapping these produces a wrong answer.

Forgetting the 2,000 GRT floor on tonnage limitations. Even if the formula calculates a lower figure, the minimum limitation is 2,000 GRT 46 CFR §11.402(b).

Assuming the Aleutian fish tender exemption is still active. It expired January 1, 2003 46 CFR §28.895(b). Exam questions may reference it as a historical rule; the correct answer is that it is no longer in effect.

Assuming a limited-tonnage endorsement holder can use §11.402(c) to upgrade. An applicant holding a national endorsement as master or mate of less than 1,600 GRT, less than 500 GRT, or less than 25–200 GRT cannot use those provisions to increase tonnage 46 CFR §11.402(d).

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Quick Check

Q1 — A T-boat with a keel laid in 1972 is 82 feet in length and operates on a domestic voyage. Is it subject to load line requirements under 46 CFR §175.122?

No. Although the vessel meets the length threshold (82 feet exceeds 79 feet / 24 meters) and the keel-laid date (1972 is after July 21, 1968), it is operating on a domestic voyage. Both conditions must be satisfied. A domestic voyage removes the §175.122 obligation. 46 CFR §175.122

Q2 — Who is responsible for verifying that a vessel complies with stability requirements before departure, and what documents must be consulted?

The master is responsible. The master must consult the vessel's trim and stability book, stability letter, Certificate of Inspection, and Load Line Certificate, as applicable. The vessel may not depart until compliance is confirmed. 46 CFR §185.315

Q3 — An applicant for an unlimited national ocean master endorsement has all required sea service on vessels of 100 GRT or more, but none of it on vessels of 1,600 GRT or more. What is the minimum tonnage limitation that will be placed on the MMC?

2,000 GRT. Even if the formula calculation produces a lower figure, the minimum tonnage limitation under 46 CFR §11.402(b) is 2,000 GRT. 46 CFR §11.402

Q4 — What service is required to remove all tonnage limitations from an unlimited national ocean master endorsement after a limitation has been imposed?

6 months of service on vessels of 1,600 GRT or more in the highest grade endorsed (i.e., as master). Providing evidence of that service removes all tonnage limitations. 46 CFR §11.402(c)(1)

Q5 — Who determines the total number of persons permitted to be carried on a Subchapter T vessel?

The cognizant Officer in Charge, Marine Inspection (OCMI). The OCMI may consider total weight of passengers, crew, and variable loads; stability restrictions; route; general arrangement; means of escape; lifesaving equipment; minimum manning; and the maximum passengers permitted under §176.113. 46 CFR §176.112

Q6 — For a Great Lakes and inland unlimited endorsement, what portion of required experience must be obtained on vessels of 1,600 GRT or more?

At least one-half of the required experience must be obtained on vessels of 1,600 GRT or more. All required experience must be on vessels of 100 GRT or more. 46 CFR §11.431