2003 outback 2.5 at times does not start when hot.

Make sure the battery cable is not eaten up by corrosion, clean and tighten the battery connections and make sure your battery is in good condition. Have the battery and alternator tested.

Guess I forgot to say both batt cables clean and secure as well as grounds. alternater and batt are new. been fighting this for a while

tomorrow I will check voltage going to start solenoid

maybe you have a bad starter relay

Yeah I was also going to say starter relay. All good suggestions to check. With age of this vehicle, you need to do voltage drop on all wires going to and from battery, starter, alternator and all grounds.

I'd double-check ground wire from engine. I've oftenb replaced the skimpy brass double-ring positive battery terminal with a solid $2 universal one, as once one of the two skinny rings cracks...or they erode away...current is limited. Note that will NOT see a voltage drop, but just current-limiting under high demand (starting).