sounds that you may have the wrong nozzle or pump pressure or the air setting is wrong or a combinatoin of all three the boul;ter 5 has a label on the burner and tells you the pump pressure and nozzle size and type
you will have to clean the soot out of the boiler first
and then work through it checking the nozzle first my advice realy would be to call your enginer back as it sounds like he has got it all wrong as the boulter boilers are realy bomb proof
littleeley
January 2011