they make special mounts just for this....they have various sizes based on whether or not its a 2 or 4 stroke and horsepower and shaft length....most online marine places sell them, so should a dealer....try defender.com.........the unit is drilled and thru bolted through the transom...some units require a backing plate to get the proper mount angle and support but thats normally for sailboats with curved transomes.....its not a big deal....