As soon as metal starts breaking or splitting from rust, the integrity of the entire trailer comes into question. There can be structural weakening inside the steel tubes that you can not see. I would replace it and if the trailer is going to see salt water, I would go with aluminum or galvanized.
2015 Seaark 1872 MV CC Etec-90
Helix 12 CHIRP SI, HB 1199, MinnKota Riptide ST80/i-pilot Link, Bob's Hydraulic
Bitter Gun Owner