Max HR

 So when reading a few of the running blogs they are often talking about what zone they want their heart rate in and then the max heart rate.  I'm still obese so I know my heart isn't going to be efficient.  but anytime I do any sort of prolonged exercise my heart rate stays in the 168-180 range.  I can still talk at that stage and don't feel awful but all the bells and whistles on the machines yell at me to slow down.  If I slow down to the levels they say I "should" be at I don't feel like I'm getting much of a work out and really don't even sweat.  

So how do I figure out where I should be?  Should I just go by how I feel and screw my HR for now?  

I would say to go by feel for now.  Personally I have never really used my HR as an indication of how hard I am working.  I do know though that if I am at 180, I am working my ass off and I am not talking to anyone.  In the 160's I am still working pretty hard and conversation is limited.  My guess is that the HR monitor is off.  If talking is possible but kind of a nuisance, you are working pretty hard.