John is it true the west side of Vashon Island the currents always flow North up Colvos Passage?
According to the literature, the answer would be "Yes". HOWEVER ... I think there are exceptions, and part of the exceptions will be that it depends on were one is in the passage. Near the shore, especially, there will be back-eddies that are counter to the main flow. Trying to either find them to help (depending on which way one is going), or avoid them, is a hit a hit-or-miss affair. I haven't been south for several years so I don't remember the details.
Going through Tacoma Narrows, though, can be a challenge because the current really flows there. Going south against the current it is best to really hug the west shore and that will really, really help. Max ebb and one is motoring along the shore against the center channel current going 3 to 4 knots and you're doing 8 or 9 knots speed over ground! Nice!!! At least up to near Point Fosdick, then it's business as usual! Going north the east shore is helpful.
The channel between McNeil Island and Anderson Island, Balch Passage, has an area where it narrows and there are rocks in the middle of the channel. It's a challenge to figure out which way to get around Anderson - clockwise or counter-clockwise, depends on winds, currents, and distance. The easy and least stressful way is to just go via the Nisqually reach.
There are counter currents all over the place in South Sound so taking notes on what works, or doesn't, and where, noting flood, ebb, or slack, will be helpful for future trips. Maps that show the bottom contours will be helpful. There are some paper current charts one can get for trip planning and digital charts can have current overlays. The digital chart that I use doesn't have the current details for back-eddies, just a big arrow indicating speed.
Back eddies can be your friend if one works them right; however, this often means running close to the shore and there can be large under-water rocks, "most" of them are marked on a nautical chart.
