That transom looks like it's been painted, and the paint is flaking off.
Do you intend to smooth out the pad area from the old wedge with Marine Tex? I don't know that I would use that for a fairing compound. It gets pretty hard and more difficult to sand once it's cured all the way.
A better choice for filling and fairing might be epoxy mixed with West Systems 407 low density filler http://www.westsystem.com/ss/filler-selection-guide/
Do you intend to smooth out the pad area from the old wedge with Marine Tex? I don't know that I would use that for a fairing compound. It gets pretty hard and more difficult to sand once it's cured all the way.
A better choice for filling and fairing might be epoxy mixed with West Systems 407 low density filler http://www.westsystem.com/ss/filler-selection-guide/