Master 100 Ton

By Captain Mike · 50 years at sea · former MITAGS faculty
Requirements checked against NMC checklists and 46 CFR · September 2026

Before you file: Requirements and NMC policy change. Open the current NMC checklist linked at the bottom of this page and confirm every number against it.

Pick the route first. It sets everything else.

"100-ton license" is shorthand for Master of self-propelled vessels of less than 100 GRT. How much time you need depends on the waters on the endorsement.

Route	Service required	Reg
Inland	360 days of service	46 CFR 11.457
Great Lakes & Inland	360 days of deck service, including 90 days on the Great Lakes	46 CFR 11.455
Near Coastal	720 days of deck service on ocean, near-coastal or Great Lakes waters. Inland time can substitute for up to 360 of those days.	46 CFR 11.428

Master 100 GRT is issued for Near Coastal, not Oceans. Up to 90 days of engine department time on vessels of appropriate tonnage can count toward the service.

Only carrying six passengers or fewer? An OUPV endorsement may be all you need, and it takes less time for Near Coastal. See the OUPV / Six-Pack guide.

The tonnage math

Having 360 or 720 days isn't enough by itself. Enough of it has to be on vessels big enough to justify a 100-ton endorsement 46 CFR 11.422. What gross tonnage means → For the full 100 GRT, you need either:

25%of the required days on vessels of 51 GRT or more (90 days inland, 180 days near coastal)

50%of the required days on vessels of 34 GRT or more (180 days inland, 360 days near coastal)

Otherwisethe endorsement is issued at 50 or 25 GRT instead, based on the same kind of calculation

Step by step

Choose route and tonnage

Decide what you actually need to operate. A Near Coastal endorsement takes twice the time of Inland. If your work never leaves protected waters, Inland may be the faster, smarter first step.

Document every vessel on its own form

For vessels of 200 GRT and under, sea service is usually documented on the Small Vessel Sea Service Form (CG-719S). The NMC requires a separate form for each vessel. A single form listing several boats will be rejected. On your own boat you'll also need proof of ownership.

Count days correctly

On smaller vessels, a creditable day can be as little as 4 hours underway 46 CFR 10.107. List only days that meet the standard. Rounding up casual trips invites a closer look at everything else you claimed.

Check recency

You need 90 days of service within the recency window. The regulation says 3 years, but CG-MMC Policy Letter 02-25 extended that to 7 years, and the current NMC checklists reflect it.

Handle the general requirements

You must be at least 19 and a U.S. citizen. You'll also need a medical certificate, drug-test compliance, and, for an original credential, a First Aid certificate completed within the past year and a current CPR card.

Take the exam or an approved course

Most candidates complete a Coast Guard-approved course in lieu of the NMC exam 46 CFR 10.403. Optional add-ons include Auxiliary Sail (360 days on sail vessels plus the sail module) and Assistance Towing.

Traps that slow down 100-ton applications

Several boats on one CG-719S. One vessel per form, every time.
Tonnage that doesn't add up. Plenty of days on 20-footers still gets you a 25-ton endorsement. Do the 25%/50% math before you apply.
A First Aid card that's too old. For an original, it has to be completed within one year of application.
Signers who can't verify. The person signing for your time should be someone the NMC can reach and who actually knows your service.
Missing ownership proof for time on your own vessel.

Already a mate on bigger ships? Mariners holding an endorsement as mate on inspected vessels of 200 GRT or more (for example Third Mate, Mate less than 1,600 GRT, or Mate OSV) can be issued Master 100 Near Coastal for the same route without additional service or exam. Evaluation and issuance fees still apply.

Who may not need it?

Six-pack operators. If you'll only carry six or fewer passengers on an uninspected vessel, an OUPV may be enough, and Near Coastal OUPV needs less sea time. OUPV / Six-Pack →
Recreational boaters who never carry passengers or cargo for hire.
Mates on larger inspected vessels. You may already qualify for Master 100 Near Coastal without more service or an exam (see the box above).

The course

Most candidates take a Coast Guard-approved Master course whose exam is accepted in place of the Coast Guard examination. 46 CFR 10.403 If you already hold OUPV, many schools offer a shorter upgrade module. Typical topics are the Rules of the Road, navigation and chart plotting, deck general and safety, and the added Master material.

The course covers the exam only. Sea time, tonnage, medical, drug test, First Aid and CPR are separate.
Check that the specific course is approved for the Master endorsement and route you want. How to check a course →

What happens after the course?

Keep the course completion certificate. Check the NMC checklist for how recent it must be when you apply.
Apply to the National Maritime Center. The NMC sets your tonnage from your documented service, so the endorsement may come out at 25, 50 or 100 GRT.
Renew every five years. Your MMC and its endorsements are valid for five years. To renew an officer endorsement like this one, you'll show one of: at least 1 year of sea service in the last 5 years; a passed open-book renewal exercise; an approved refresher course; or qualifying closely related work or instructing. 46 CFR 10.227 Renewal & Continuity →

THE CAPTAIN SAYS…

Do the tonnage math before you pay for the course, not after. A course certificate won't turn days on small boats into a 100-ton endorsement. If you're short on bigger-boat time, the fix is time on bigger boats.

Moving up to bigger boats? Master less than 200 GRT needs time as Master or Mate while licensed, and time on larger vessels. Master 200 Ton →

Ready to apply? Applications now go through Navita, the Coast Guard's online credentialing system. It changes how you apply, not what you need. Navita: what changed →