Honda BF15D BF20D Outboard Motors Shop Manual., Page 367Get this manual
7) Lean the power tilt assembly to the side as shown with
the piston rod fully compressedPush the "UP" side of the power tilt switch and extend the piston rod approximately 50 mm (2 in) from the end of the piston rod8) With the power tilt assembly inclined to the side, add the ATF to the oil tank slowly until the fluid flows out of the oil filler port by using syringe or equivalent tool
[I] Extend approx50 mm from
the fully compressed position[2] Add the ATF up to the edge of the oil filler port
9) Push the "UP" side of the power tilt switch with the power