Gather all ingredients.

Combine pineapple juice, sugar, eggs, flour, and 1/2 teaspoon salt in a saucepan. Stir and cook over medium heat until thickened.

Remove from heat; stir in lemon juice. Let cool to room temperature, about 1 hour.

Bring a large pot of water to a boil; add oil and remaining 2 teaspoons salt. Add pasta and cook until al dente, 5 to 7 minutes. Drain and rinse under cold water.

Combine cooked pasta, cooled egg mixture, mandarin oranges, pineapple tidbits, crushed pineapple, and whipped topping in a large bowl; mix well. Refrigerate until chilled, 8 hours to overnight.

Before serving, add marshmallows and coconut; toss and serve.