Regal LS4 Owner's Manual page 44

Navigation Rules
An overtaking boat is burdened, and is not the
privileged craft, even though it approaches the
danger zone of the overtaken boat.
The overtaking boat fi rst signals with a single
blast if that boat desires to pass on the starboard
side of the boat ahead, or a double blast if
passing to port. The overtaken craft responds
with the same signal if safe, or with the danger
signal (5 short blasts or more) if unsafe. The boat
overtaking must not pass unless the appropriate
signals are sounded.
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