I have not talked to the man personally but I have been told that some of the better prop shops will repair skegs. I actually watched a youtube video of a man making a repair. Looked like factory when he finished.
Good welders will snap/TIG them back off/on. A little grinding and some fairing, it looks like new.
:edit:
Like this: http://www.youtube.com/watch?v=HVS6qfveLG4
Just ignore his advice on replacing the prop with stainless "It's strong"... yes, and you'll be replacing the lower unit's input shaft instead of the prop next time.
Depends how far off-line it is ... if the bottom of the skeg used to be at 6 o'clock and it is now at 5 or 7 ... personally I wouldn't lose sleep over it, but that's me. Note it could be causing some counter-steering, so be aware of that, and where your LU trailing fin is positioned.
Just ignore his advice on replacing the prop with stainless "It's strong"... yes, and you'll be replacing the lower unit's input shaft instead of the prop next time.
My prop shop has hanging the wall what's left of a yamaha LU after a skeg guard strike that would have resulted in just a bent or sheared skeg sans the skeg guard. IMO while the skeg guard may be a quick and cosmetically pleasing repair that may even to some appear to be an "upgrade" to a factory intact skeg, keep in mind use of this product makes the LU the sacrificial component rather than the skeg.
FWIW my prop guy says the skinny water guides whose props he services/fixes all use a rigid plastic bolt on type skeg similar to the skeg guard but retains the skegs sacrificial design. I don't have any particular info on it other than what the prop shop guy mentioned.