I'm a 58 year old. had open inguinal hernia mesh repair surgery. job requires lifting 75-150 lbs. how long is recovery before going back to this job?

Depends a lot: on size of hernia and integrity of your tissues. Only your surgeon would know details. The usual period of recovery for intense physical activity is 2-3 weeks. Ask your surgeon for specific recommendations.

If you want after 4w: Healing will be near complete after collagen tissue i is formed i that will take place 3 Wks , most of the people will go back to work in 4 to 6 wks. obvious other factors , your motivation , general health , non healing etc will limit early return to work . When you go back obvious you will not going to lift 150 lbs on first day , has to be progressive.