How to Tow Another Vessel

Seamanship · Emergency Procedures

Towing another vessel is one of the seamanship skills that looks straightforward until you are actually doing it. The disabled boat is often in an awkward position, its crew may be stressed, conditions are usually not ideal, and the mechanics of transferring a tow line across open water without fouling propellers or causing a collision require precise boat handling in close quarters. Add the fact that cleats fail, lines part, and towed boats yaw unpredictably at the wrong speeds, and you have a procedure worth thinking through before you find yourself in the middle of it.

Before any of the mechanics: the Good Samaritan question.

The Maritime Obligation to Render Assistance

Maritime law in most jurisdictions — and international SOLAS convention — establishes a legal duty for masters of vessels to render assistance to anyone found at sea in danger of being lost, provided it can be done without serious danger to the rescuing vessel or crew. This is not a courtesy. It is a legal obligation, and declining to assist a vessel in genuine distress when you could safely have done so has consequences.

The key qualifier is "without serious danger." You are not obligated to put your vessel on the rocks or your crew at risk to help someone else. If conditions are such that attempting a tow would endanger your boat and crew, you are not legally required to attempt it — you are required to report the distress on VHF 16, provide whatever assistance you safely can (such as standing by), and coordinate with the Coast Guard. The obligation does not require recklessness.

The practical upshot: if another vessel signals distress within range, and you can help without undue risk, the default answer is yes. Know the Good Samaritan framework before you decide. A recreational boater who passes a distress signal without responding and something bad happens to the people aboard is in a difficult position legally and morally.

Making Contact and Assessing the Situation

Hail the vessel in distress on VHF Channel 16. Establish: what the problem is, how many people are aboard, whether there is any immediate danger beyond the engine failure or gear issue, their GPS position if they have it, and what their anchoring situation is. A vessel that is safely anchored in calm water is a different problem from a vessel drifting onto a lee shore in 20 knots of wind.

Once you have the picture, advise the vessel what you intend to do and ask them to prepare a tow line on their bow — through the bow fairlead (the chock at the bow, not just a cleat) if they have one, with the bitter end secured to their most structural forward point. If they do not have a bow fairlead, they should run the line around the mast base or through the anchor locker if it is forward enough. The line should be led so the tow point is at or near the centerline of the bow, not offset to one side.

Approach slowly, upwind or upcurrent of the disabled vessel. Do not come alongside until you understand the wind and current vectors — two drifting boats coming together have more momentum than they look like they do.

Rigging the Tow Line: What Will and Won't Hold

The most common mistake in improvised towing is attaching the tow line to a single cockpit cleat on the towing vessel's stern. Cockpit cleats are designed for dock lines and sheet leads — loads that are mostly static or moderate. A tow line under a shock load from a 10,000-pound displacement boat surging in chop is a different order of magnitude. Cleat base failures in this scenario are well-documented and dangerous: a cleat that tears out under load takes a chunk of deck with it and sends hardware flying.

The correct attachment on the towing vessel is to a primary winch, a through-bolted deck fitting, or a dedicated tow post if the vessel has one. Better still is a bridle: run two lines from port and starboard strong points (genoa car tracks, primary winch bases, or well-bedded stern cleats with backing plates) and join them at the centerline before attaching the tow line. A bridle distributes the tow load across the stern of the vessel rather than concentrating it at a single point, and it keeps the tow tracking true behind the centerline rather than pulling the stern to one side.

Use your longest available nylon line — minimum 150 feet in open water. Nylon stretches under load, which is what you want: the elasticity absorbs the shock when the towed vessel's bow drops into a trough and the line comes tight. Polyester (Dacron) is less ideal but acceptable. Polypropylene — the floating yellow rope — is a poor choice for towing because it lacks the stretch to handle shock loads and fatigues quickly at the knot.

150 feet is the minimum in open water because shorter lines put the towed vessel at risk of surfing down a wave and running into your stern. When the towing vessel is in a wave trough and the tow is at the crest, a short line allows the towed bow to override you. In protected water or flat conditions, shorter lines are manageable, but in any seaway, err toward more scope.

Towing Speed and Behavior

Three to four knots is the practical ceiling for recreational towing. The physics are straightforward: every displacement hull has a hull speed determined by its waterline length (approximately 1.34 × the square root of the waterline in feet, in knots). At or above hull speed, bow wave resistance increases dramatically. The towed vessel's bow wave creates a stern pull that, above about 4 knots, translates into yawing — the stern of the towed vessel swings side to side, imposing shock loads on the tow line and creating a risk of broach. If the towed vessel broaches, the load spike on the tow line is sudden and severe.

Accelerate slowly from a stop. The worst moment is the initial load when the slack comes out of the tow line — a sudden jerk is hard on both the line and the attachment points. Bring the tow line to tension gradually by motoring forward gently before applying throttle. Once underway, maintain a steady speed and avoid sudden course changes, which swing the towed vessel on the line and cause yawing.

Watch the tow in your mirror or assign someone to watch it continuously. A vessel that starts to yaw significantly needs slower speed, not more throttle.

Communication During the Tow

Before you start moving, establish a communications protocol with the towed vessel. Agree on: the VHF working channel you will both monitor, the speed you intend to maintain, a hand signal system if VHF is unavailable, and — critically — the emergency release procedure.

The towed vessel must understand what to do if the tow line parts. The towing vessel must understand what to do if the tow line must be cut — and cutting must be possible instantly. Keep a sharp knife rigged at the tow attachment point, accessible without crawling. If the towed vessel suddenly grounds, broaches, or another emergency develops, the towing vessel must be able to release the line before the momentum of the towed vessel drags the towing vessel into trouble as well.

The towed vessel's crew should be kept away from the bow while under tow. A parted tow line under load snaps back with dangerous force. Brief them before you start.

Entering Harbor and Handing Off

Shorten the tow line significantly before entering a harbor or marina — 30 to 50 feet is typical for maneuvering in close quarters. A long tow line in a tight space makes steering the tow unpredictable. Call ahead to the marina on their working channel (typically Channel 9 for recreational marinas) to advise that you are arriving under tow and need a berth assignment and dock assistance. Most marinas will provide a hand to take lines.

If the disabled vessel has any steering or propulsion at all — even partial — coordinate with their crew to use it. Even light rudder correction on the towed vessel can prevent the yawing that makes the final approach into a slip difficult.

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Frequently Asked Questions

What is the maritime legal obligation to render assistance and when does it apply? Maritime law in most jurisdictions — and international SOLAS convention — establishes a legal duty for masters of vessels to render assistance to anyone found at sea in danger of being lost, provided it can be done without serious danger to the rescuing vessel or crew. This is not a courtesy but a legal obligation. The key qualifier is 'without serious danger': if conditions are such that attempting a tow would endanger your boat and crew, you are not legally required to attempt it — you are required to report the distress on VHF 16, provide whatever assistance you safely can, and coordinate with the Coast Guard. A recreational boater who passes a distress signal without responding and something bad happens is in a difficult position legally and morally.

Why should you never attach a tow line to a single cockpit cleat and what is the correct attachment? Cockpit cleats are designed for dock lines and sheet leads — loads that are mostly static or moderate. A tow line under shock load from a 10,000-pound displacement boat surging in chop is a different order of magnitude, and cleat base failures in this scenario are well-documented and dangerous: a cleat that tears out under load takes a chunk of deck with it and sends hardware flying. The correct attachment on the towing vessel is to a primary winch, a through-bolted deck fitting, or a dedicated tow post. Better still is a bridle: run two lines from port and starboard strong points and join them at the centerline, distributing the tow load across the stern rather than concentrating it at a single point.

What tow line material and length are required for safe open-water towing? Use your longest available nylon line — minimum 150 feet in open water. Nylon stretches under load, and that elasticity absorbs the shock when the towed vessel's bow drops into a trough and the line comes tight. Polyester (Dacron) is less ideal but acceptable. Polypropylene — the floating yellow rope — is a poor choice for towing because it lacks the stretch to handle shock loads and fatigues quickly at the knot. 150 feet is the minimum in open water because shorter lines put the towed vessel at risk of surfing down a wave and running into your stern: when the towing vessel is in a wave trough and the tow is at the crest, a short line allows the towed bow to override you.

What is the maximum safe towing speed and why does exceeding it cause problems? Three to four knots is the practical ceiling for recreational towing. Every displacement hull has a hull speed determined by waterline length — at or above hull speed, bow wave resistance increases dramatically. The towed vessel's bow wave creates a stern pull that, above about 4 knots, translates into yawing — the stern swings side to side, imposing shock loads on the tow line and creating a risk of broach. If the towed vessel broaches, the load spike on the tow line is sudden and severe. Accelerate slowly from a stop; the worst moment is the initial load when the slack comes out of the line. Watch the tow continuously: a vessel that starts to yaw significantly needs slower speed, not more throttle.

What emergency procedures must be established before beginning a tow? Before starting, establish with the towed vessel: the VHF working channel you will both monitor, the speed you intend to maintain, a hand signal system if VHF is unavailable, and the emergency release procedure. The towing vessel must be able to cut the tow line instantly — keep a sharp knife rigged at the tow attachment point, accessible without crawling. If the towed vessel suddenly grounds, broaches, or another emergency develops, the towing vessel must be able to release the line before the towed vessel's momentum drags the towing vessel into trouble. A parted tow line under load snaps back with dangerous force; brief the towed vessel's crew to stay away from the bow while under tow.