The parts diagrams at www.shop.evinrude.com don't show an electric start, but I remember plenty of electric start 18hp ERudes over the years. My guess is that your motor has a factory option package. I wouldn't call it a "conversion," because that usually implies installation of parts not originally designed for the motor.
Depends on the year. For 1968, all 18's came from the factory as rope start and electric start was an accessory kit. It was offered in two types: Self-contained with a start button on the motor, and remote with start and choke at the forward olcation.
