If you're attempting to remove the whole assembly - swivel bracket with clamps - then you'll need to pull the powerhead. The earliest 15/18 style motors didn't have access to the front motor mount without pulling the powerhead and belly pan off. Beyond that, it's fairly straightforward. Remove the 2-piece horseshoe at the base of the swivel (nut on the outer, two bolts visible, two slotted bolts recessed). Remove the nuts off the two upper motor mounts. Remove the nut from the front motor mount. Helps to have two people, as sometimes if you have broken mounts, the motor can get floppy at this point. Lift the lower unit out of the upper mounts by tilting the leg away from the swivel. The upper mounts should pop free of the steering bracket.