Each boat will require 3 feet across to fit itself and 2 feet space on one side for a total of 2+3 = <<3+2=5>>5 feet per boat
The last boat will need an additional 2 feet space on its other side, so this 2 feet should be subtracted first from the 42 feet which leaves 42-2 = <<42-2=40>>40 feet
5 feet per boat on the remaining 40 feet for a total of 40/5 = <<40/5=8>>8 boats
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