Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 401Get this manual
HONDA BF25A
TRANSOM DRILLING
Verify that no damage will occur when the motor mounting holes are drilledLook for any structural impediments such as bulkheads, braces, fuel cells, bilge pumps, or floor sections before drilling1Using the drawing below, measure and mark the four 2center marksBe sure that the upper bolt holes are closer than in(32mm) from the top Of Ihe actual boat transomDo not mark or drill the upper holes in wooden block attached to the top of the boat transomMark the lower bolt holes so that the mounting bolts contact the upper end of the stem bracket