luke warm water........
*When gas heats how long does it take.....time between gas on/gas off?
*What is temp AT the water heater vs at a faucet?
*T-stat should open at 130*F/140*F (Brand Dependent Suburban/Atwood)
*Did you change Bypass setting...cracked open?
*Showers....if hot/cold knobs left open/lever-button on handle closed the faucet will mix hot/cold
*Dip tubes inside the WH Tank......if fallen/broken off will cause dilution of hot out due to loss of 'thermal zone' within the tank (Suburban can be replaced/Atwood NO)