Where exactly is the ? (e.g., the winch frame, the trailer stand, or the gears?)
The cracked area must be ground down to bare, clean metal. The crack itself should be "V-grooved" (ground into a V-shape) to allow the weld to penetrate fully.
Mount the new winch with stainless steel bolts, washers, and nylon-insert lock nuts. Torque bolts evenly. Do not overtighten—that can distort the base plate. Apply marine grease to the gear access port (if present).
However, if you confirm a true metal crack, do not rationalize it. Do not "keep an eye on it." Do not wrap it in duct tape. A trailer winch under a 2,500 lb load stores immense kinetic energy. When the crack gives way, that energy releases as a metal shard flying at bullet speed.
