Neutral and Idle detents
If your engine control looks like the pix above, it could be an old Morse, now apparently out-of-production.
Internally, the contol is a series of disks sandwiched together around a central splined shaft. The detents for neutral on the transmission bell crank and for idle on the throttle bell crank are accomplished by spring-loaded balls and holes. That is, steel balls about 1/4 in. dia are pushed into slightly undersize holes in the adjacent disk.
If your shifter is sloppy, you may have lost your balls.
If that's the case, it could be an easy fix.
Joe - s/v Assignment, Catalina 320