Hi Andy:
Welcome to HK Outdoors!
As to question – I’d guess over 20 mins, Wong Shek to Tai Long Wan; and not much more to Long Ke Wan (which is just a little past it; time to here maybe similar to time from Sai Kung to Long Ke).
Just emailed a couple of Sai Kung speedboat owners, asking them, so hope for expert answer shortly.
Cheers,
Martin