To check for rot I take a small hammer with a flat face or a pocket knife, and begin tapping around lightly on the transom beginning in the top outside corners. This is usually a solid area and you will hear a sharp sound when you tap. Moving in inches go towards the holes in the transom, motor bolts, transducers, drains for bilge and splashwell and listen for the taps to dull and sound spongy. Get my drift? Also, remove the transom saver, trim the motor level, and add a significant amount of weight on the end of the decavitation plate, above the prop, and look for movement between jack plate and transom, or motor and transom if no jack plate. Better if someone else adds the weight and you look for the movement. Mine cost a serious chunk of change to replace, But I felt the boat was worth it.
Creativity is just intelligence fooling around