4 meter = 12.8 feet.
12 Ft is too low for a 250 MH fixture, depending on the type fixture. Is this a flood light or a downlight?
I suspect a flood light.
LED equals to 250 watt MH do not exist, yet, to my knowledge.
If this is a downlight, you can use something equal to a 175 watt MH:
http://www.lumec.com/pdf/series/LifeLED_brochure_an.pdf