3/4 cup water
1/3 cup soy sauce
2 tablespoons sugar
1 teaspoon ground ginger
1 teaspoon dried crushed thyme
1 clove garlic, minced
1 boneless rump roast, about 1.5kg
Combine water, soy sauce, ginger, sugar, thyme, and garlic in a large, sealable, food storage bag (large enough to hold rump roast).
Pierce rump roast all over with fork; place in bag. Close bag and turn to coat rump roast thoroughly. Seal and refrigerate rump roast at least 4 hours or overnight. Turn bag occasionally.
Remove rump roast from bag; return marinade to refrigerator.
Place rump roast on a rack in shallow pan. Roast rump roast, uncovered, at 165° for about 2 hours, basting with marinade during the last 30 minutes.
Strain remaining marinade and add 2 tablespoons of water; bring to a boil in a saucepan and boil for 1 minute.
Spoon marinade over the sliced rump roast and serve with your favourite roast vegies.