Difference between Go by the board and Go overboard

go by the board—

1. (also: come by the board) fall into the water from a ship:

• The ship gave a tremendous roll … and the mast went by the board.

2. said of an idea or an activity no longer practiced (often with the implication of regret):

• Now, within recent years the old materialism of our fathers has gone by the board.

go overboard—

1. = go by the board 1:

• During the storm a lot of the deck cargo went overboard.

2. (coll.) lose one’s senses; go mad:

• My uncle has been acting very strangely recently; the family think he may have gone overboard.

3. be very enthusiastic about smth.; do more than is necessary:

• Many teachers have gone overboard for the new methods without considering their worth.