This company offers motors and pumps for sale from its Web site, as well as from a new location in Chelsea. From generators and capacitors to air compressors and pumping systems, Williamson is a one-stop shop for all your motor needs. The business was founded in 1944 in Brookline and about 10 years later moved to Needham, after which Williamson continued to grow and move through generations of the family. It also does custom work, including changing voltages and rebuilding control panels.