I have a Yamaha 9.9 which is heavy mounted on my transom. Been there for 10 years. When it was mounted I had a piece of 1/4" thick aluminum mounted inside the boat. The boat is a SeaSport which has a transom that is about 1 and 1/1" thick or more. The bracket was then bolted through the transom and the aluminum plate. Have never had a problem. I would caution you to use a rope or bungie to lash the motor to something on your transom though, otherwise the steering arm will swing it back and forth all the time.