Believe me I understand what happened to you. I mounted a fox 52cc gas engine to a 4x4 post in the ground to test run the engine, It had a 20x10 mejzlik prop on it, after some adjusting & priming I got it running, I started throttling up until it was just about peaked & three of the screws holding the engine to the post pulled out. the engine swung really fast away from me & broke the last screw, it fell to the ground killing the engine. Luckily it swung away from where I was standing & I didn't get hurt, as a matter of fact neither did the engine or prop. I guess I was very lucky. After that I drilled some holes completely through the post & used some long bolts with washers & double nuts to test the engine. I wish you would have been as lucky as I was.

Gil