Shops do it as part of the rigging But make sure they first epoxy the inside of the holes let dry and then use 5200 to help keep out the water. The bolts must be drilled on the same angle as the transom so they use a guide to maintain that angle. New motor shops have a stencil they use to mark the holes first.
FellowShip
………………………….
Just for the Grins
Official Antique Classic SeaCraft Owner