Re: 1978 Johnson Electric 35hp External Wiring Harness
That '78 internal harness should be equipped with a large black plug to connect the control. If it does, you need an external harness with a black plug. Motors built after 78 or 79 used a red plug on the harnesses and they won't mate with the black ones. You can start the motor easily without the harness but you can't stop the motor easily without some way to short the ignition, which is one of the things that the harness and ignition switch provide. These harnesses are relatively expensive, even used and harnesses with the black plugs are kind of rare to find used. The factory uses these plug-in harnesses to facilitate ease of installation and standardization of controllers that can be used on many different motors. The same thing can be accomplished with the main + - battery cables and a 3 conductor cable to facilitate starter control, choke control, and ignition shorting, but basic electrical knowledge would be required to get that done but it is relatively easy. If you want to find a harness new or used, I'd go to Ebay first. I have seen them there for $100 -$150 but make sure you get the right color plug.
