John L.Hamer;76;of Belle Vernon;died Wednesday;Jan.7;1998 at home.  A steel mill worker by trade;he was a veteran of World War II and an elder in the Marion Presbyterian Church in Fairhope;where he was active on the dartball team.  He was a member of the American Legion Post 659 in Belle Vernon.  He is survived by his wife;Sarah;two sons;James Hamer of South Park and Bruce Hamer of Middletown;two brothers;Allen Hamer of Belle Vernon and Willard Hamer of Charleroi;one sister;Emma Jean Dunn of Belle Vernon.  Services will be held at the convenience of the family.