Mercy Ships currently operates the largest non-governmental hospital ship in the world, staffed “mostly by volunteers,” said David Warner, 67, a two-decade, full-time volunteer with the organization that started in 1978. Warner, a U.S. Navy veteran, found a natural home in the maritime mission after his military service and 12-year stint as an Amazon river boat captain, volunteering in the remote Brazilian jungles. He likes that Mercy Ships offer free medical services “to the world’s forgotten poor, on a much bigger scale.” In June, he will observe his 25th anniversary with the medical ministry. “You know, it’s easy just to tell someone God loves them,”  he said at his East Texas home on Jan. 4, “but it’s harder for them to hear it if they are ostracized in their villages because of some medical defect such as a tumor, or can’t walk because of bone issues. “Once they have surgeries the …