The water ballast
weighs 1400 pounds, so that would be an instant drop to a possible top
speed of only 10 MPH according to the MacGregor website (1 MPH drop
for every 100 pounds added.) That's with all the other caveats (one
person, no rigging, etc) remaining.

So with a crew of 4 adults, food and water and other supplies, the 26M will
actually do -4 knots.

RB