The stern-drive, or inboard-outboard motors, were available both as separate units for boat-builders, or as components of boats produced by OMC. Built to give the fuel economy and dependability of inboard engines, they were nevertheless as versatile as outboards. By 1965 the company was selling only about 20,000 stern drives a year, however, and sales of the outboards were still outpacing them tenfold. The problem stemmed from the engine's state-of-the-art technology; many dealers did not know how to repair these motors, and owners were often ignorant of maintenance needs. OMC met this challenge by developing computerized week-long repair and maintenance classes for dealer training. Four schools, two permanently stationed in San Francisco, California, and Waukegan, Illinois, and two mobile units familiarized customers with the new engines.