Hi Pigwig,
You don't want to be pushing the tide at all if you can manage it. Use the flood to get up as far as you can, I think from memory it is a good 6nm from the mouth of the river to Rivergate alone, then on to hamilton reach and the city. There used to be a race up to Dockside, if you missed the tide in a 4knot weapon you'd be tacking backwards and forwards without moving. It used to take you all day to get there sailing from Manly.
The river is closed for Riverfire, from before the story bridge and upwards from memory.
Edit: see below map for river closures.