J70TLEND 92 70hp Johnson won't idle

I have the above on my skiff. It no longer idles. Seems to run great once I pop it in gear, but as soon as I throttle back to nuetral it stalls. Also, what is the purpose of the red valve on the starboard side of the motor. Where should it be positioned. It seems to be adjusting the choke, or fuel volume.
Thanks,

The red valve is on the primer solenoid. It should be turned down, pointing at the bottom of solenoid.