Replaced the two elements 3800watts ( old one burned out) now I only get a little warm water? The water heater is a interthern nordyne In152dhmte 240volt single phase

I give up. If someone were to walk up to you and ask the question you just listed, what do you think their answer would be, a blank look, maybe?

Just thinking about the electrical connection components, the only way this can be answered is by checking the connection voltage from the supply branch circuit to the control on the water heater.

At the water heater, there should be 120 Vac between the ground and each hot conductor. There should be 240 Vac measured across both hot conductors.

Hot water heaters have controllers that control the heating elements. Normally only one element is on at the time. With a clamp on Ammeter, make sure both elements are drawing the correct amperage.

Low hot water temp would be caused by low voltage, bad controller, mistaken connections on the replaced element or the second element being defective also.