Subchapter M: What Towing Operators Need to Know

Ten years after it took effect, Subchapter M is no longer a new regulation. It is the operating framework for the entire U.S. towing industry, and the phase-in that occupied everyone's attention between 2016 and 2022 is long finished.

What has replaced it is a renewal cycle, and that cycle is producing a specific set of problems right now for operators who obtained their first Certificate of Inspection early. Requirements that were deferred for five years are coming due, and the consequence of missing them is not a deficiency notice. It is a COI that does not get renewed.

This article covers what Subchapter M is, who it applies to, what compliance actually requires, and what is biting operators in 2026. The choice between the two compliance pathways is a separate subject with its own analysis, and we will address it in a follow-up piece.

What Subchapter M Is

Subchapter M sits at 46 CFR Parts 136 through 144. It was published in the Federal Register on June 20, 2016 and took effect the following month, establishing for the first time a comprehensive inspection regime for towing vessels, which had previously operated as uninspected vessels.

The reach of the regulation is broader than many operators appreciate. It supersedes OSHA jurisdiction over covered vessels, and it preempts state regulation of vessel design, construction, alteration, repair, maintenance, operation, equipping, personnel qualifications, and manning. For an operator running boats in Louisiana and Texas waters, this means the applicable safety framework is federal and uniform rather than a patchwork.

The phase-in ran six years. New vessels with keels laid after July 20, 2017 had to comply in full. Existing vessels had until July 20, 2018 for most requirements, with the COI deadline running to July 19, 2022. That schedule is now complete, which means every covered vessel operating today should hold a valid COI.

Who Is Covered

Under 46 CFR 136.105, the subchapter applies to all U.S. flag towing vessels engaged in pushing, pulling, or hauling alongside, subject to exceptions.

The primary exception is size. A vessel under 26 feet in length, measured end to end over the deck excluding the sheer, is outside the regulation. The Coast Guard adopted the length standard from 46 U.S.C. 8904(a) after considering and rejecting alternatives based on tow size, displacement, and shaft horsepower, on the basis that length is more administratively manageable even though it is a less direct measure of risk.

That size exception has a significant carve-out. A vessel under 26 feet is not excepted if it is pushing, pulling, or hauling a barge carrying oil or hazardous material in bulk. The Coast Guard clarified this specifically in response to comments on the proposed rule. All towing vessels involved in the movement of oil or hazardous material barges in bulk, regardless of size, must be certificated and manned in accordance with their COI.

For Gulf and inland operators, that carve-out matters. A small boat moving a loaded oil barge is inside the regulation even if an identical boat doing harbor assist work is outside it.

Other exceptions exist for certain categories of operation. Fleet boats present a specific case. A fleet boat may fall outside the requirement provided it operates exclusively within a Limited Geographic Area as defined in 46 CFR 136.110, as determined by the local Captain of the Port, and meets the excepted vessel provisions coordinated with the local Officer in Charge, Marine Inspection. That exception depends on both a COTP determination and OCMI coordination, so it is not something an operator can simply assert.

The regulation also creates a category of excepted vessel, meaning a vessel that is subject to the subchapter but excepted from certain provisions within it. Excepted is not the same as exempt, and the distinction is worth confirming rather than assuming.

The COI Is the Operative Document

A towing vessel must be in full compliance with a valid COI aboard in order to operate. The Coast Guard may issue a temporary COI while a permanent one is in progress, but there is no version of lawful operation without one.

The COI itself describes the vessel, the routes it may travel, minimum manning and total persons allowed aboard, required safety equipment and appliances, horsepower, and any other information the OCMI considers pertinent to the vessel's operations. It is valid for five years from the date of issue.

Obtaining one runs through 46 CFR 136.210. The owner or managing operator submits Form CG-3752, Application for Inspection of U.S. Vessel, to the cognizant OCMI where the inspection will take place. The application must be submitted at least 30 days before the initial inspection for certification, and the inspection itself must be scheduled at least three months in advance.

One point that catches operators out on the front end. A drydock or internal structural examination is not required before the initial COI is issued. The Coast Guard has confirmed this in its published FAQs. Neither the Coast Guard nor a third party organization is required to attend a drydock before initial certification.

Two Pathways, Both Ending at the Coast Guard

Under 46 CFR 136.200, there are two options for documenting compliance in order to obtain a COI.

The Coast Guard option means all inspections of the vessel are conducted by the Coast Guard. An operator choosing this route may use a management system, vessel operations manual, towing vessel record, or logbook to meet the recordkeeping requirements.

The TSMS option means compliance is documented through a Towing Safety Management System, with a third party organization conducting audits and surveys.

Two things are true regardless of which route is chosen. The Coast Guard issues the COI in either case, and the Coast Guard may board a vessel at any time to verify compliance and take appropriate action. The choice affects who conducts routine inspections and how deficiencies are documented, not whether the Coast Guard retains authority.

The choice is made per vessel rather than per fleet. An owner or managing operator must specify on the inspection application which option applies to each particular towing vessel, which means a mixed fleet can run both.

Which route makes sense for a given operator depends on fleet size, operating profile, existing safety management infrastructure, and cost tolerance. That comparison deserves its own treatment and we will cover it separately.

What Compliance Actually Requires

The substantive requirements are spread across Parts 140 through 144, and they are more extensive than the pre-2016 uninspected regime by a wide margin.

Part 140, Operations: Towing gear and towing safety requirements, marine casualty reporting, official logbooks, and specified items to be recorded. This part carries the operational discipline that the Coast Guard viewed as central to addressing the human element in towing casualties.

Part 141, Lifesaving: Survival craft, stowage, lifejackets, immersion suits, visual distress signals, and line throwing appliances, with requirements varying by route and service. Survival craft requirements can be adjusted where the OCMI or an applicable TSMS determines they are not necessary, and a compliant skiff may substitute for some required equipment.

Part 143, Machinery and Electrical Systems: This part contains two requirements that are creating problems right now, discussed below.

Part 144, Construction and Arrangement: Structural standards, watertight and weathertight integrity, and hull thickness measurement. For existing vessels, minimum gaging requirements follow the recommendations in NVIC 7-68. For new vessels, 46 CFR 144.205(d) requires the selected structural standard to be applied throughout the vessel including maintenance and alterations.

Drydock and Internal Structural Examination: Regardless of which compliance option is chosen, every towing vessel must undergo drydock and internal structural examination at specified intervals once it holds a COI. A vessel exposed to salt water more than six months in any twelve month period since the last examination or initial certification must be examined at least twice every five years, with no more than 36 months between examinations. Freshwater vessels are on a less frequent cycle. For Gulf Coast operators running boats that move between brownwater and saltwater service, tracking salt water exposure is a compliance obligation in itself.

What Is Biting in 2026

Here is the item most likely to matter to an operator reading this today.

Under 46 CFR 143.200(c), no later than five years after issuance of the first COI for the vessel, all existing towing vessels inspected under Subchapter M must meet the Pilothouse Alerter requirement at 46 CFR 143.450 and the Towing Machinery requirements at 46 CFR 143.460.

The Coast Guard's Office of Commercial Vessel Compliance has been reminding operators of this, and the consequence is spelled out. Failure to meet these requirements could result in issuance of a CG-835V vessel deficiency and possibly non-renewal of the five year COI under 46 CFR 136.215.

First COIs began issuing in 2018 and the deadline for existing vessels ran to July 2022. Five years after those dates lands between 2023 and 2027. Every vessel in the fleet is either past that threshold, at it, or approaching it, and the renewal is where it gets tested.

A pilothouse alerter installation is not a same week job, particularly if the vessel is working and the yard schedule is tight. An operator who discovers the requirement during the renewal inspection has a boat that cannot get its COI renewed and no quick path to fixing it.

Deficiencies and Documentation

How deficiencies get recorded depends on the compliance route and on who is present.

Deficiencies identified by a vessel's third party organization are documented by the TPO in accordance with the vessel's TSMS. Where both the TPO and the Coast Guard are present, the TPO documents them under the TSMS, with the exception of an inspection for certification. Deficiencies identified during an inspection for certification, which occurs once every five years, are documented by the Coast Guard.

That last category is the one with teeth, because it is the inspection that determines whether the COI issues.

The Insurance Dimension

Subchapter M status is not solely a regulatory matter, and operators sometimes miss its effect on their insurance position.

Underwriters treat a documented safety management system as a favorable risk characteristic. An operator running a mature TSMS with clean audit history, complete towing vessel records, and no pattern of repeat deficiencies presents differently to a hull and P&I underwriter than one operating on the minimum.

The reverse also matters. Operating outside the terms of a COI, or operating without a valid COI, raises questions about the insured's compliance with warranties and with the general obligation to operate lawfully. Where a casualty occurs and the vessel was operating in a condition or on a route the COI did not authorize, the coverage position is not something to be exploring for the first time during the claim.

There is also a straightforward evidentiary point. The records Subchapter M requires you to keep, logbooks, towing vessel records, maintenance documentation, and casualty reports, are the same records that establish what happened when a claim arises. An operator with disciplined Subchapter M recordkeeping is better positioned in a liability dispute regardless of the regulation, because the contemporaneous documentation exists.

Practical Steps:

Confirm applicability vessel by vessel. The under 26 foot exception and the oil and hazmat barge carve-out interact in ways that are specific to what each boat actually does. A fleet where some boats move loaded oil barges and others do not may have vessels on both sides of the line.

Check the five year clock on every COI. Identify the first COI issuance date for each vessel and calculate the pilothouse alerter and towing machinery deadline. If any of those dates are inside twelve months, that is a yard scheduling problem to solve now rather than a compliance question to answer later.

Track salt water exposure. The drydock and ISE interval depends on it, and the tracking obligation sits with the operator.

Verify your fleet boat exceptions are documented. A Limited Geographic Area exception requires a COTP determination and OCMI coordination. If your file does not contain evidence of both, the exception may not hold.

Review your COI terms against actual operations. Routes, manning, persons aboard, and horsepower are all specified on the certificate. Operations that have drifted beyond those terms are a compliance exposure and potentially an insurance one.

The Bottom Line

Subchapter M turned towing vessels from uninspected craft into inspected vessels operating under a federal certificate, and it did so on a phase-in schedule that gave the industry six years to adapt. That period is over.

The regulation is now in a steady state where the operative question is not whether you are in the regime but whether your certificate will renew. For operators approaching the five year mark on their first COI, the answer to that depends on requirements that were deferred and are now due, and the time to address them is before the inspection rather than during it.