IMO the amount of vertical motion developed at the transom even in a small sea is enough to have the prop constantly in and out of the water. Keep in mind that the distance from the cavitation plate and the prop is less than a foot.
Given that the OB motor is kind of out of reach it is clear that the throttle will be set to a given RPM, directionally locked and the boat steered on it's own rudder.
There is little question in my mind that the OB will overspeed again and again as the prop clears the water then gets buried again. I wouldn't bet any money on the durability of the OB. (or the transom
I don't believe it to be a workable solution unless you're in a very flat-water environment. I agree with Cam, in emergency make the dingy fast and push the yacht with that.