Re: Need Wiring Diagram for 1966 40hp Evinrude RKL-28B
I have a 63 RKL-25 with a faulty generator and carry a spare battery, basically the same motor as yours. Lower unit requires voltage to power electromagnets in gearcase to remain in gear. In addition to generator, it would also have had a regulator which was in a junction box mounted in the boat near motor.
Generator that fits this motor is an autolite or prestolite 10amp unit. Both regulator and generator are a pricey. regulator can still be obtained if you look around a bit, generator more difficult to find. Asking price for generator typically over $100 and $75 for generator, and you would need special belt which is another $60ish.
might be easiest to run with extra battery in boat and look for parts motor that has your missing parts.