Due to recent financial setbacks, I'm cooking a lot more.  Also due to financial setbacks, i'm cooking crappier cuts of meat.

so:  how do you moist cook a pot roast?  I've got the dry roast stuff down well, but the dry roast doesn't work for the tougher cuts i buy these days.  I follow the recipies fairly closely--but here's the thing I don't get.  They always say to cook the darn thing for 4 hours or so.  According to my thermometer, after and hour and a half at 300 degrees f, surrounded by liquid halfway up the roast, the roast is now like 140 degrees according to my thermometer, and now strong enough for me to fix my boys shoes with. 

I know i've done a couple of things wrong, like not bringing the liquid to a boil on the stove before going in the oven.  I don't have a crock pot, and i'm not sure about the small roasting pan i'm using on the burner.  it's kinda old and thin already.

Am I cooking the darn thing too long or not long enough?  Or do i just have to cope with tough roast? 

I'm using rump roasts and round roasts, eye of round, the cheap cuts.  Cest la vie, if we're going to eat beef now, it ain't gonna be prime rib.  (though i did get some on sale once.  yum.  haha)

TIA guys.  common, help out a non betty crocker.