OK, after doing a few more calculations, I still feel like there's something "off" about the ship movement table, and I'm wondering if there's some mixture of movement in feet and movement in yards listed here.

First, here's a rough conversion list based on distance and time conversions:

10.7 knots ~ 60 yards/rnd ~ 180 ft/rnd ~ 83 mi/day

8.9 knots ~ 50 yards/rnd ~ 150 ft/rnd ~ 69 mi/day

7.1 knots ~ 40 yards/rnd ~ 120 ft/rnd ~ 55 mi/day

5.3 knots ~ 30 yards/rnd ~ 90 ft/rnd ~ 42 mi/day

3.6 knots ~ 20 yards/rnd ~ 60 ft/rnd ~ 27.6 mi/day

1.8 knots ~ 10 yards/rnd ~ 30 ft/rnd ~ 13.8 mi/day

This is based on the conversion factor 1 knot ~ 1.15 mph ~ 13.8 mile/day, which assumes 12 hours of travel per day. I've also assumed that rounds are 10 seconds.

Based on those numbers, it looks like ships that travel around 72 miles/day are probably traveling at about 9 knots, a bit optimistic but not impossible for a quality sailing ship in good wind. That corresponds to a speed of 150 ft/round. If we look at the ACKS table for a large sailing ship, however, we see a combat speed of 45'. This looks much more like the correct speed in "yards/round", rather than ft/round. Incidentally, B/X and BECMI both list this as 150', so it was decreased by a factor of 3 for some reason in ACKS, not just copied from those earlier sources.

On the other hand, ACKS does use speeds of the 120' to 150' for galleys in combat, which feels just about right in ft/round. They should be able to sprint up into the 8-10 knot range for short times. As noted above, this looks like a correction in ACKS from the B/X and BECMI values, which seem obviously wrong. They have sailing speed for galleys being higher than rowing speed -- which might possibly be true outside combat, but certainly not during combat. I'm not sure about speeds in miles per day. ACKS optimistically lists galleys at 40-50 miles/day, but B/X thinks they can only make 12-18. I would have guessed somewhere in the middle, about 20-30 miles.

So at this point my assessment is that ACKS fixed galley speeds, but at the same time introduced an error in sailing speeds, possibly due to giving values in yards/round rather than ft/round. (It's possible this adjustment is related to some other correction factor, but I'm not sure what kind of correction would only reduce combat speeds but not daily movement...) I'm curious to see if there's anything I missed, but otherwise I think I'm going to house rule the sailing ship speeds back to B/X speeds. This gives them much better odds to escape a galley, unless caught upwind or without any wind at all.

If Alex is around, I'd be very interested in the rationale behind the changes from older editions.