Changing UNO Rev3 chip from Atmega328-PU to Atmaga328P-PU

I replaced the my Uno Rev3 chip do a new one. It came with a pre-loaded bootloader and a default sketch that blinks. I uploaded a new sketch and it runned pretty good. But, when I turn the Uno OFF and ON again, the sketch that runs is the default one (that blinks) instead of the new one.

I looked forward directions, including parameters for changing the chips, but nothing solved the problem. I have 2 of them and both runs in the same way.

Any advice ? Thx in advance.

I think that's a bootloader bug. Try uploading the Optiboot bootloader.