The cruise port is called Circular Quay. From circular quay you get 1 train to Central and the Mercure is an easy few minutes walk from there ??
That should of been a smiley face st the end not question marks lol
Agree - contact Concierge at hotel.
Try the concierge at the Mercure - I live in Tokyo do any estimate I could make should be taken with a grain of salt.