We have a 2 year old Minimax Heater by Pentair.
Last year the water coming from the heater was HOT.
This year it's like bath water. Tech guy came out and said it is working the way is should and the water is warm enough. He is trying to tell us that nothing is wrong with the heater. It takes 7 hrs to raise the water temp 3 degrees. Last year the temp rose a lot quicker.
Anyone have any ideas?
Thanks!

That was likely the outfit who sold you the unit and not a Pentair rep. Try this site to see the specs for your unit and talk to customer service. Pentair Water Pool and Spa