Unless your cables or control box have gone south it should be an easy enough adjustment at the motor end. If you get it adjusted and then everything seems to change then look for an issue in the cables or the box.

Browns Point won't be able to help with the johnyrude, they are a Suzuki dealer. Ishop Marine, boats.net and some others are a good online parts source for OMC. If it's a tiller with the switch in the arm your probably going to need an oem part to get the right fit, remote control about as bad. If it's in the front of the pan a generic switch will usually fit. Solder any joints that might get made, the crimps will let you down.