16 hp Go-devil Long tail (short shaft - 58")

Ive noticed that my motor has gotten real wobbly on the transom. I just give the tiller a little budge and the motor wobbles back and forth.

I tried tightening that bolt right under the u-joint on the swivel bracket and it wouldnt budge, maybe I just wasn't giving it enough elbow grease..?

1) Could the wobbling of the motor have to do with prop depth being off?

2) Any recommendations on getting motor to stop wobbling/ prop depth set right?

Seems self explanatory typically when somethings loose it just needs to be tightened but the only thing I could see to do was to tighten the bolt on the swivel bracket.

Is your handle tight? The four bolts under the engine plate? I've had those vibrate off before and feel "wobbly".