Originally Posted by PaulM
...but he must maintain course and speed. Is this correct?
Usually, but not necessarily so as it is a mistake to take it literally.
If sailing under an implementation of the International Regulations
for Preventing Collisions at Sea the tests generally considered are -
A. Is the manoeuvre of the stand on vessel an ordinary and proper one that would require a change in direction or speed?
B. Is the manoeuvre which the stand on vessel undertakes one that could reasonably be foreseen by the give way vessel?
So, for example, the stand on vessel can change course and speed (noting that "course" does not infer a compass
course) in order to avoid a danger
- that one hopes is probably pretty obvious. It may also be that the stand on vessel could legitimately change course to enter a side channel, for example, as long as the give way vessel could reasonably have foreseen that. It might also be that if one is overtaking a vessel rounding a headland with constant helm
on that the give way vessel's changing course is a course being maintained ie you maybe cannot expect him to go to straight ahead helm
at some time in order to meet the requirements of maintaining course and speed while you pass or cross.
The originating test case often quoted was one in which the stand on ship stopped to pick up a pilot - this was judged to be both ordinary and proper, and foreseeable by the give way vessel and gives a good sense as to the types of action that the stand on vessel can take.
Whether either of the tests applied in your own case I don't know but would seem if there is nothing relevant that you have not said then the give way boat was in the wrong. I mention the above as is a common misconception that the stand on vessel has always to hold course and speed - if I am the give way vessel I always exercise caution in case of course or speed change by the stand on vessel.