Need Any Welding advice?

I was going to ask JUST one question, before all panties got in a wad!
Stepson has a big bass boat. Other day, he found the "bracket", yes it is big , that holds the BIG outboard, was cracked. It is cast aluminum. I also noticed that it is not just bolted together but some of it is welded.
Aluminum stock trailers are mig welded. What is the system to weld this cast aluminum? Just curious.