How hot should the water leaving my central heating boiler be?

Most boilers run at around 75 to 80 C. If your house is not getting hot you have a few things to consider. 1. is house thermostat working. 2. is the boiler thermostat actually working or is it cutting off at low temp. 3. most systems have what is called a motorised valve. This valve diverts water to where ever the call for heat is. If this valve is no opening then water will not be circulating. This valve is normally located near boiler in a galvanised box. On one end is a lever that you can move to over ride the valve. Sometimes these get stuck after not being used all summer. CH system should be kicked in once a month to keep it up and running. 4. Is the circulation pump running. Put your hand on it and feel for vibration. Hope this somehow helps.