78 johnson 35HP Starter Issue

Hello. I have a 78 Johnson 35HP motor that got matched up with an Evinrude throttle assembly at some point in the past. It worked just fine for a couple years. Sometimes in the past, the ignition wouldn't turn over...no click or anything. A pro boat mechanic told me since it's an old motor, to "jiggle" the throttle hand back and forth. He was right...it worked. I'd rock the handle back and forth a few times then the motor would start right up. Now, it seems instead of 1 or 2 times of rocking the handle back and forth, it takes several attempts. Sometimes it takes 20 attempts of moving the handle back and forth. The boat was just in the shop and sat outside in the weather for 3 months waiting on them to do the carb repair. The first time I had the boat back in the water and it didn't start, it would click but not engage the starter motor so I sprayed some WD-40 down the starter motor. If fired up so I figured it may have been gunked up since it sat for so long at the shop. But it still isn't starting up the way it used to. I've checked the battery and cleaned the terminals. Replaced the battery cables because the old ones were severely corroded (bare wires!), and just replaced the starter solenoid. I've checked the ground connections, too, and they seem solid. I keep thinking it's something up front with the throttle assembly. I always assumed there was an electrical connection in the throttle but apparently there isn't; just the throttle cables. So my question is there a sort of contact point that needs to be bridged when you operate the throttle handle?

There is a switch ( neutral start ) on the motor shift linkages.-----Needs cleaning ( easy to do ) or adjustment.