Starboard To Starboard Passing: Safe Boating Guide

Navigating tight channels, busy harbors, and open water requires absolute clarity when another vessel approaches. While standard maritime convention prioritizes passing port-to-port in head-on situations under COLREGs Rule 14, specific circumstances, narrow channels, and overtaking scenarios demand a precise understanding of starboard to starboard passing. Misinterpreting right-of-way rules or miscommunicating your intentions on the water leads to close quarters, wake turbulence hazards, and serious collisions.

Mastering starboard to starboard passing means knowing exactly when standard rules apply, how to initiate sound and visual signals, and how to account for vessel dynamics like pivot points and displacement wakes. This guide breaks down the legal framework, tactical execution steps, and critical mistakes to avoid so you can handle complex traffic encounters with total confidence.

Understanding Navigation Rules and Right-of-Way

Maritime navigation is governed globally by the International Regulations for Preventing Collisions at Sea (COLREGs) and nationally by the U.S. Coast Guard Navigation Rules. Knowing how these rules dictate passing maneuvers prevents dangerous assumptions on the water.

In a head-on or nearly head-on situation where two power-driven vessels meet so as to involve risk of collision, each vessel must alter her course to starboard so that each passes on the port side of the other under COLREG Rule 14. However, a starboard to starboard passing typically occurs in two distinct scenarios: To see the complete picture, we recommend the excellent report by The New York Times.

• Overtaking Situations: Under COLREG Rule 13, any vessel overtaking any other must keep out of the way of the vessel being overtaken. While an overtaking vessel can generally pass on either side in open water, passing safely on the starboard side of the lead vessel requires clear communication and adequate sea room.
• Narrow Channels and Fairways: Under COLREG Rule 9, vessels proceeding along the course of a narrow channel or fairway must keep to the starboard-side outer limit of the channel that is safe and practicable. If local currents, shoals, or obstructions require two boats to pass starboard-to-starboard, specific sound signals and mutual agreement are mandatory.

Pre-Pass Assessment: Evaluating Risk Before You Move

Never attempt a passing maneuver without first scanning the environment and evaluating vessel performance factors. Skipping assessment steps leads to misjudged closing speeds and sudden emergency maneuvers.

1. Calculate Closing Speed and Aspect: Observe the heading and speed of the other vessel using a compass bearing ring or radar. If the compass bearing of an approaching vessel does not change appreciably, a risk of collision exists.
2. Examine Waterway Constraints: Check depth sounders, chartplotters, and local buoys. Ensure there is enough lateral clearance outside the channel markers to execute a wide berth without running aground.
3. Assess Environmental Factors: Strong crosswinds, tidal currents, and heavy chop alter handling characteristics. A heavy displacement cruiser passing a smaller planing hull at close range creates suction and displacement wakes that can swamp or destabilize the smaller boat.

Step-by-Step Execution of a Starboard-to-Starboard Pass

When conditions require passing starboard-to-starboard, precise execution keeps both crews safe. Follow these operational steps:

• Establish VHF Radio Contact: Use VHF channel 16 to switch to a working channel (like Channel 68 or 72) and explicitly state your intentions. Say, “Vessel off my starboard bow, this is [Your Boat Name]. Requesting a starboard-to-starboard pass.” Do not alter course until the other skipper explicitly confirms understanding and agreement.
• Sound Maneuvering Signals: If radio contact isn't established, use your horn in compliance with COLREG Rule 34. Two short blasts indicate your intention to direct your course to port (passing starboard to starboard). Wait for the answering two short blasts from the other vessel before acting.
• Alter Course Early and Substantially: Make a clear, unmistakable heading change to port so your starboard side faces the other vessel's starboard side. Avoid timid, incremental steering adjustments that confuse the other operator.
• Maintain Safe Lateral Separation: Give the other vessel a wide berth. In open water, maintain a distance of at least three to four boat lengths depending on your speed. In restricted channels, balance clearance with safe navigation limits.
• Reduce Speed to Minimize Wake: Ease back on the throttle as you draw abeam. Excessive wake slamming into a passing boat creates loss of control risks, particularly for paddlecraft, sailboats, and smaller motorboats.
• Return to Course Safely: Hold your modified heading until you are well clear of the overtaken vessel's stern wake before returning to your original course line.

Common Mistakes to Avoid on the Water

Even experienced skippers make critical errors during passing situations. Avoiding these pitfalls keeps your vessel out of trouble:

• Assuming Agreement Without Signals: Never assume another boater understands your silent intentions. Passing without a positive VHF response or horn confirmation is a primary cause of head-on collisions.
• Failing to Account for Dead Zones: Larger commercial vessels have massive blind spots forward of their bow. If you are overtaking a tug and tow or a large yacht, ensure you can see their navigation bridge and that their radar operator acknowledges you.
• Riding the Wake Too Closely: Cutting back in too sharply right after clearing the bow of a passed vessel subjects your stern to dangerous reactionary currents and surf-zone broaching effects.
• Ignoring Local Navigation Rules: Certain rivers, lakes, and port authorities enforce specific local bylaws that override standard passing customs. Always review local notices to mariners.

Frequently Asked Questions

When is a starboard-to-starboard pass legally required?

It is rarely required by default, as standard head-on rules mandate port-to-port passing. However, narrow channel geography, shallow shoals, bridge construction zones, or mutual agreement via radio horn signals can make a starboard-to-starboard pass necessary and legal.

What sound signal indicates a starboard-to-starboard pass?

Under inland and international rules, two short blasts of the vessel's horn indicate an intention to direct your course to port, signaling a starboard-to-starboard passing arrangement.

Who has the right of way in an overtaking situation?

Under COLREG Rule 13, the vessel being overtaken has the right of way. The overtaking vessel must remain clear of the overtaken vessel's path until completely past and clear, regardless of which side is chosen.

How do I handle passing a sailboat under power versus sail?

If a sailboat is operating under sail alone, it generally has the right of way over power-driven vessels under COLREG Rule 18. Give sailboats an exceptionally wide berth, as their maneuverability is restricted by wind angles and tacking limitations.