[RS]

Putting a new motor on an old hull, I would not use a template. Get a lift and some help, and maybe some wood shims. Put some masking tape on the transom to mark the center, and maybe a few strips an equal distance to the sides to help with visual alignment.

Depending on your setup, someone can probably tell you where the ventilation plate needs to be in relation with the bottom of the hull. Your mounting holes should allow for some adjustment to that. Very important - be certain that the hole location on the inside of the transom will not compromise the splash well or access hatch (if any).