1966 SRV 170, Johnson electroshift controls??

[1966sv170]

First Sea Ray boat, first post on Club Sea Ray...
I bought a project boat a few months ago basically a hull and a box of parts. It's back together, running well, and low and behold it floats!! I just took it out in the water and although it'll run, I can't seem to figure out the relationship between the FWD/RVS shifter and the small-red lever on the back of the shifter. It has an arrow and says "start". The boat will not start without the red lever being in the back or "start" position (no surprise there) and the once it's in gear and going it runs better when it's forward. but the shifter will not return to neutral if the red lever is forward. So I have to pull it back if I want to put it in neutral or reverse. It's not a choke because the engine has dual carbs with automatic choke. If someone has seen this before could you explain exactly what the red lever does, how it interacts with the shifter, and whether it's working the way it's supposed to?
It has a 2.5L Chevy 4cyl. inboard w/OMC 400 outdrive.
Thanks for your assistance.

 

[offduty]

It sounds like it may be the idle adjustment that you would use when your starting the boat. Have you tried moving the lever while the engine is running to see if the rpm's go up and down?

 

[1966sv170]

Yes the rpm's do go up and down. Does it electrically alter or retard the timing? I'm still not sure why it would keep the main shift handle from going back into neutral when it's up though. I have found an exploded view of the shifter assy but it doesn't help much. I was considering taking it apart to see how one lever effects the other. I'm an engine guy not a boat guy so I'm not really familiar with how any of these shifters work other than pushing forward makes you go forward and pulling back makes you go back.
Thanks for your assistance.