I know this thread is old, but I've been digging and digging to find out more about my project boat. I have a 1975 johnson 50hp 2 stroke. I am having the exact issue. These pics look identical to mine.
Issue: no idle
The trick I was shown to get it going is: spray starter fluid, flip the warmup lever all the way up, turn the key, hold the toggle switch up and then throw the accelerator lever all the way forward. The boat will go after that. If I slow down too much, it'll die. Idling in neutral first never works.
Jacob645, were you ever able to fix the issue permanently?
I don't know much about outboards, but I'd really like to be out n the water this season. I am technically minded and can fix just about anything. Any pointers would be greatly appreciated.