Depending on how bad and where the crack is located specifically. A lot of these have been sucessfully repaired with a good cold weld compound, such as Marinetex or Belzona. You should avoid welding whenever possible as this puts tremendous heat thru the aluminum and usually causes warpage to the machined surfaces inside creating problems for the bearing races. Make sure the area to be repaired is ground down to metal, clean with Lacquer Thinner, and you should be fine.