As I may have been partly responsible for this thread, via Strobes, I feel more confident here to iterate I was taught to yell 'Clear Prop!' and give a decent, useful pause after.
In the US, it was 'Clear!' but both sides of the pond the emphasis was on the same thing: make a big noise and make it count.
There will never be numerical proof of its eficacy, but I don't care.
Besides, where else does one get encouraged to yell like a fishwife? I was never good at Ladylike; this makes sense in more ways than one.
