Cut zucchini in half lengthwise and carve out the middle, leaving about 1/4 inch of flesh around the sides so that the zucchinis will still keep their shape. I used a spoon to scrape out the middle.
Brush zucchinis with olive oil and place in a casserole dish.
In a large mixing bowl, mix together ricotta cheese, and parsley, mozzarella and parmesan cheese until combined.
In a skillet over medium-high heat, brown ground turkey and drain any excess grease. Mix ground turkey with marinara sauce.
To assemble zucchini boats: evenly fill zucchinis with cheese mixture so that the bottoms are covered but that the cheese is not higher than the sides of the zucchini. Finish by topping each zucchini with meat and marinara mixture.
Cover baking dish with foil and bake zucchini boats for 30 minutes. Remove foil and sprinkle tops of zucchini boats with mozzarella, then bake uncovered for an additional 5 minutes. When ready cheese should be melted and zucchinis should be soft.