If your lemon pie gets watery then you may have not used enough cornstarch in the lemon pie or you forgot to use cornstarch in the lemon pie and it turned out watery.
The lemon pie needs cornstarch which is a good thickener for lemon pie.
If you used cornstarch in your lemon pie and yet it's still watery you need to use a bit more cornstarch in the lemon pie recipe to make it thicker.
I had that problem with the lemon pie becoming watery and my mom told me to add some additional cornstarch to the lemon pie and it came out better.
So try adding some more cornstarch to the next recipe when you make another lemon pie and it should turn out not watery.