Place potatoes and water in a microwave safe bowl. Cook potatoes in microwave on high until just tender, about 15 minutes, stirring half-way through. Drain potatoes and allow to steam for a few minutes to dry. In a large bowl, stir together mayonnaise, wine, rosemary, and garlic powder. Mix in drained potatoes and toss to coat. Marinate, covered, in the refrigerator for 1 hour. Preheat an outdoor grill for high heat and lightly oil grate.