Pat shrimp dry, devein, and set aside. Set up three bowls: flour with salt, garlic powder, and pepper; whisked eggs; and breadcrumbs mixed with Parmesan cheese.
Heat oil in a skillet to 375°F (191°C). Bread the shrimp by dredging in flour, dipping in eggs, and coating in breadcrumbs. Fry in batches for 2-3 minutes per side until golden. Transfer to a wire rack to drain.
Spread marinara on a baking sheet, arrange fried shrimp, spoon sauce over, and top with mozzarella and Parmesan. Broil for 5 minutes until cheese is melted and bubbly.