can a galaxy 250w ballast run 150 watt bulb
 

as it tells,

would it be ok to conect a 150w hqi to a 250w galaxy ballast (as my 250w bulbs are on order and wont arive in a while

I do believe the 150W bulb would blow up, too much power to it.

Bulb go BOOM!

never had in mind thy wouldsay boom, I almost try'd it, in tghis case I have to wait

Ya I;'ve seen it at work where someone has replaced with lower wattage. Get about 2 months then it just exploded one day. Good thing it was inside another glass shade.

So for MH's the ballast forces the current rather than the bulb drawing it?

That's pretty much it.

Kinda, the higher the wattage, the higher the ballast voltage and the more current will flow through the lamp. A lower wattage lamp will run much hotter, which cracks the glass