What year model is your tug? I've got the same year/model as Seakr25 and have a 9.9 yamaha high thrust mounted on the step. First I just mounted it to the plastic step with a bolt on mount. That was pretty shaky. I ended up spanning the gap between two of the supports with ss square stock. Much better but the step still deforms due to the torque when the motor is running. I've used it that way for three seasons but am now in to process of re-designing it again. The mount needs either be directly over one of the supports or rigidly span all the way between two of them. Definitely recommend you go with a motor with a 25inch foot. The cavitation plate on the motor needs to be within an inch or so of the bottom of the boat. Otherwise it will ventilate in choppy seas.
