The Scots battled to a 21-15 win over Swaziland to move top of section one after the previous leaders, South Africa, were edged out 16-17 by Fiji.
"It's a nice position to be in and sets us up for our clash with South Africa later today," the Scottish skip, Gourlay, said.
Scotland also led the pairs table with Julie Forrest and Joyce Lindores beating Botswana's Babs Anderson and Helen Graham 15-13.
England moved into eighth place after Gill Fitzgerald and Norma Shaw recovered to beat Guernsey's Jean and Anne Simon 18-14, with Shaw back in the line-up after pulling out on the previous day through sickness.
The defending champions, Phillis Nolan and Margaret Johnston of Ireland, stayed in contention when they coasted to a 33-7 win over Argentina's Maria Vasquez and Gladis Merli. They lie third in their table behind the unbeaten South Africans and Namibians.