Brown meat and mix with garlic powder, bread crumbs, salt, onion salt, Italian Seasoning, pepper, and 1/2 cup Marinara sauce. Fill manicotti with the meat mixture. Pour half of the Marinara sauce in 9 inch x 13 inch casserole dish. Lay in manicotti and cover with remaining sauce. Bake about 40 minutes in 350 degree oven.