Preheat the oven to 450 degrees F (230 degrees C).

Combine marionberries, 3/4 cup sugar, flour, and lemon juice together in a large bowl.

Place 1 pie crust in bottom of a 9-inch pie plate; add marionberry filling. Cover with remaining crust; crimp edges to seal. Brush pie lightly with water. Sprinkle remaining 2 teaspoons sugar on top. Cut 4 to 8 slits (1-inch) in top crust with a knife.

Bake in the preheated oven for 10 minutes. Reduce heat to 350 degrees F (175 degrees C); continue baking until crust golden, 45 to 50 minutes more. Let cool completely before serving, about 1 hour.