mine was the sensor, the revs dropped, S/C wouldn't engage all the time. Didn't seem to matter. I have a johnson pump setting on the bench, but haven't needed yet. But I as well thought, electrical, anything but the S/C...but that was what it turned out to be. Taking it to a dealer is your only option unless you have the knowledge and tools to work on it. If it threw a code, then a local parts store can read it. I bet one or the other. Mine was the temp sensor....they replaced the pump first...so I have a new bosch, but johnson is in reserve...good luck..