The boiler cleaning apparatus and method provides for cleaning the exterior surfaces of a heat exchanger. The apparatus and method include tools and steps, respectively, for temporarily spreading tubes and holding open the tubes to gain access to tube lanes. Once access to a lane is attained, a nozzle assembly having an outlet for blowing high velocity cleaning fluid is selected from a group of nozzle assemblies. The selected nozzle assembly will have an outlet for blowing fluid in a direction that effectively cleans the tubes adjacent the opened lane. After the tubes are cleaned the tool for holding the lane opened is removed and the process is repeated for another lane.