On December 30, 2022, during my first solo voyage to Izu Oshima, I experienced violent boat movement that I did not understand at the time.
Only afterward did I come to think that it may have been broaching.
This article is not a technical explanation of broaching. It is a record of what I felt when, as a beginner, I suddenly encountered boat movement I could not understand, and what I learned from it.
Izu Oshima: One of the First Open-Sea Destinations From Tokyo Bay
Izu Oshima is the largest of the Izu Islands, located south of Tokyo.
For boaters leaving Tokyo Bay, it is one of the first destinations where they encounter conditions that feel more like the open Pacific.
Habu Port, which is used by pleasure boats, is located at the southern end of the island. Reaching it means passing through the waters south of Izu Oshima.
The straight-line distance from my home marina on the Miura Peninsula to Habu Port is about 24 nautical miles. In calm conditions, the distance itself is not especially difficult, but the sea state around the southern side of Izu Oshima can be quite different from that inside Tokyo Bay.
After taking delivery of my boat, I had focused on practicing four things:
- Departure and docking
- Ropework, including cleat hitches and bowlines
- Operation of GPS, radar, and autopilot
- Gradually expanding my cruising range
On the morning of December 30, after checking a stable weather forecast, I decided at 6:00 a.m. to head for Izu Oshima.
South of Izu Oshima, the Boat Suddenly Stopped Feeling Like Mine
As I approached the southern side of Izu Oshima, the waves became larger.
Then the boat suddenly yawed hard and heeled.
It did not feel like ordinary rolling.
For a brief moment, the boat no longer felt like something I was controlling. It felt like something being moved by the sea.
I thought the boat might roll onto its side, and I felt intense fear.
At the time, I did not understand what was happening.
All I knew was that the boat had moved in a way I had never experienced before.
And that frightened me.
That feeling is what stayed with me most strongly from the experience.
It May Have Been Broaching
Broaching is generally described as a sudden yaw caused by following or stern-quartering seas, in which a boat can no longer maintain its intended heading.
The boat may heel severely, and in serious cases the motion can lead to a knockdown or capsize.
Later, after reading about broaching and watching related videos, I realized that several aspects of my experience seemed to match:
- A sudden, large yaw
- Strong heeling
- A feeling that the relationship between helm input and boat response was different from normal
However, I did not accurately record the wave direction, wavelength, boat speed, trim, throttle position, or other conditions at the time.
For that reason, I still do not say with certainty that it was broaching.
I think it may have been broaching.
I Suspect Outboard Boats May Be More Resistant to Broaching
My boat is powered by twin outboard engines.
On a conventional shaft-driven boat, propeller thrust is basically fixed in direction, while a separate rudder changes the boat’s heading.
On an outboard-powered boat, the outboard units themselves turn from side to side.
In other words, the direction of propeller thrust itself changes to steer the boat.
As far as I know, there is no direct research comparing the resistance of outboard-powered boats and shaft-driven boats to broaching in stern-quartering seas.
However, mechanically, it seems reasonable to me that an outboard-powered boat may have an advantage.
As long as the propellers remain sufficiently immersed and continue producing thrust, an outboard-powered boat can direct that thrust against an unwanted yaw.
So, if other conditions are similar, I suspect that an outboard-powered boat may be more resistant to broaching.
Of course, this is my own inference based on the steering mechanism.
Actual broaching resistance will vary greatly depending on hull design, boat speed, wave direction, trim, weight distribution, propeller immersion, and other factors.
An outboard-powered boat is not immune to broaching.
What I can say with certainty about my own experience is simply this:
The boat yawed and heeled faster than I could understand and correct it.
Entering Habu Port
After that, I continued carefully toward Habu Port.
During the approach, I realized that I had forgotten to disengage the autopilot and quickly switched it off.
Inside the harbor, a highly experienced senior boater took my lines, and I docked safely.
After checking the remaining daylight, fuel, weather, and sea conditions, I decided that I could return to my home marina.
The return trip was much easier.
The waves were lower, and I was able to cruise comfortably in the afternoon sunlight.
The only problem was that I lost one fender. The knot I had used while docking had not been secure enough.
The Biggest Lesson Was Not Knowing What Was Happening
This voyage taught me several practical lessons:
- Check whether the autopilot is on or off
- Secure fenders properly
- Learn more about following and stern-quartering seas
But the biggest lesson was something more basic.
While it was happening, I did not know what was happening.
Knowing the word “broaching” is not the same as understanding what it feels like when a boat suddenly yaws and heels.
With experience, a boater may gradually learn to distinguish between ordinary surfing, manageable yaw, and a more dangerous loss-of-control situation.
But on December 30, 2022, I could not make that distinction.
Conclusion
I reached Habu Port and returned safely to my home marina.
The voyage itself was a success.
But the strongest lesson I brought back was this:
Boat movement you cannot identify can be very frightening.
Only later, after learning the word “broaching,” was I able to give that experience some shape.
Some parts of seamanship cannot be fully understood from books or videos alone.
Sometimes, you only begin to understand them when the boat itself shows you what they feel like.
