Gross Tonnage for TUGs


Can anyone explain me why a lot of tugs are 299 GT and not 300 GT or 310 GT?

Why does this threshold matters?

Thank you in advance for your help.

Best regards,

Prior to subchapter M you had uninspected towing vessels. By regulation they had to be less than 300grt. Anything larger was a ship and had to have a Certificate of Inspection, which comes with inspections and Manning requirements. So ideally everyone wanted to be an uninspected towing vessel to avoid “most” of the hassles of owning, running and maintain a ship.

Now with subchapter M most tugs are or will be “inspected” by the Coast Guard, and eventually have a COI. Most of the larger companies and many smaller ones like mine have COIs for their tugs, which subjects them to the same scrutiny as a ship, albeit on a somewhat smaller level.

In the US there is also a license scheme especially for towing vessels where the licenses are somewhat easier to get than licenses to operate ships.

Not really. A towing vessel endorsement requires sea time, an exam, and practical demonstrations (TOAR). All other licenses only require sea time and an exam. STCW is different, but all towing vessels on international voyages, and any towing vessel over 199 GRT outside the boundary line (including domestics voyages, also require STCW.

Also, to qualify as a mate for towing vessels, it’s possibly faster to get a mate 500 license and complete a TOAR than it is to go through by towing vessel endorsements (Mate 500 N/C is 2 years, mate towing vessel via apprentice mate is 2.5 years).

Yes, but also remember that in addition to the Certification and Manning parts for US Flag vessels- there was also the 90 M rules in classification- this was usually a near coastal, not as stringent rule srt… But I have to agree on the base point- the 200 and 300 GRT and under rules were for years- quite different…

Tonnage is a fictional and nonsensical measurement system that is full of loopholes and exceptions, it has little to do with reality.

As I recall, the Officers Competency Convention required more officers with higher qualifications for seagoing tugs over 300 tons. So there were virtually no seagoing tugs over 300 tons.

The USCG uses “regulatory” GRT, rather than ITC GT. It’s a meaningless measurement with no basis in reality.

Previously, tugs over 200 GRT required licensed engineers. Therefore, there were very few tugs were over 300 tons.

There use to be licenses called “Operator of uninflected towing vessels” for tugs under 200 GRT, and “Master (or Mate) Freight and Towing” for tugs over 200 GRT. The “operator” licenses were much easier to get, so there were not too many tugs over 200 GRT. Tugs under 200 tons can also have a two watch system with fewer crew.

Most tug owners now want even greater “rule beater” tugs under 100 GRT. 130 foot, 5000hp tugs are being built at 99 GRT. These tugs can be legally run by two officers with just two more guys off the street with no seamen’s papers at all.

Subchapter M is not a serious inspection program. It is a pathetic joke and appeasement of owners and lobbyists masquerading as an inspection program. It is a soft glance, not a hard look, at the safety condition of tugs.

Worst of all, Subchapter M codifies the undermanning of tugs.

Subchapter M pretends to greatly enhance tug safety and covers up its total failure with a blizzard of useless paperwork.

Towing licenses are far too easy for people with just a one day TOAR simulator class and a 500 license to get. It only takes 30 days of actual tugboat seatime. Time which is often spent as a temporary tug deckhand chipping and painting with no real tug operating experience value.

On the other had the “hawsepipe” Apprentice Mate route to a towing license takes three years, which is far too long for anyone with wheelhouse potential. It’s much cheaper and faster for anyone with half a brain to get a 500 ton license first, then do the 30 days and a one day TOAR class.

For an example: a fisherman friend has no towing experience, but he has Master 1600 Oceans. He took a one day TOAR simulator class, then spent 20 (12 hours days) as a deckhand on a tug (half of it was chipping and painting tied up alongside the office). He now has Master of Towing Oceans.


^^^ nailed it. Big scheme to increase profit margin for ownership is what it boils down to…

ITC was approved by IMO in 1969 (52 years ago)
ITC 69 went into force in 1982 (39 years ago), with a 12 year grace period for existing ship.
Since 1994 (27 years ago) the GT and NT indices have been the only official measures of ships’ tonnage.
Except in the US.
Apparently IMO membership and compliance is regarded as selective to USCG. (??)

Refr, Guard Insight No. 208, 2012:

Apparently IMO membership and compliance is regarded as selective to USCG. (??)
The US is a rogue nation when it comes to compliance

Correct me if I’m wrong, but the old U.S. regulatory tonnage rules apply only to vessels in domestic trade. That is, they do not call at foreign ports. Therefore the vessels would not need to follow international (IMO) rules.

The company I work at has five vessels. Four list ITC tonnages on their documentation. One lists only what we call GRT, shorthand for tonnage under the domestic rules.

They do travel through Canadian waters on innocent passage, but that is not the same as international travel (our vessel don’t clear customs, because they go from American port (Seattle) to American (Alaskan) port).

You are correct. I honestly wonder how many other countries have separate schemes for domestic tonnage vs international tonnage, It has always been a mystery to me. A five pound bag of sugar displaces the same amount of water whether within the waters of the USA or in the middle of the Pacific Ocean.

I’ve never had , or heard of, a problem going to foreign ports with a tug that is only measured in GRT. Not in Panama, Canada, Mexico , or the Caribbean.

Now, most tugs have dual measurement in both domestic GRT and ITC GT. For regulatory purposes the USCG uses GRT.

The 99 ton tugs, passenger boats, and OSVs, and 199 ton fishing vessels keep getting bigger and bigger as they are designed to exploit all the loopholes in the tonnage rules.


I tried to Goole it, but the answer was not very clear.I found NONE that still used GRT/NRT

AFAIK ITC 69 has been adopted by all IMO members for both international, domestic and fishing fleets, with the exception of the US.

PS> The USCG “Clarification” issued in 2010 did not do much to clarify anything AFA I could understand. (Without spending a lot of time on it)

A few years ago I was told by a surveyor that only the U.S. and China had a domestic tonnage system, in addition to using the international one. As I said, that was second-hand info.

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The USA and China only? Makes sense in a humerous way.

Now why would that be?


In 1980 , China acceded to the International Convention on Tonnage Measurement

A total of 141 States are parties to this Convention representing 98.61% of the world tonnage

Don’t worry the US will eventually transition to ITC tonnage. Probably in another 50 years.

Recent Sub M inspection noted that only GRT/NRT was on some paperwork, while the tug had both ITC and domestic. This raised some sort of red flag, about sailing foreign, including Canada, and was an error that had to be corrected at CG HQ.
The ITC needed to be included to sail foreign

Worked on some quite large tugs. 5600 to 10k hp. They were all registered 199 tons or less for whatever reasons or bulkhead arrangements. It truly was a science/scam to obey the class rules at the time. Had more than enough license to accomodate if the tonnage measurements changed. Didn’t bother me a bit.

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When I was with Chouest back in the 1990s. They were going to change some of the tonnage measurement rules. Chouest laid down 16 keels in their yards, anywhere there was room. So when built out they would be measured under the old rules.

Even some of the newer units I have been on were equipped with “tonnage” doors, to prevent the space from being measured as tonnage.

I don’t get how its legal or even safe, but they continue to do it.