OMC Cobra Shifting Problem.

I was hopeing some seasoned techs here could help me with a question
regarding my OMC Cobra shifting problem.
It's a 1993 Stearndrive with a 4.3 6 cyl.
I noticed last season that I was getting the typical clunk sound when
going into either foreword or reverse gear. The boat has always done
that since I have owned it (3 years now) and I thought it was normal.
I found out differently however.
I do have an OEM service manual (not clymer) and have gone through the
adjustment procedures 3 times. The switch for killing off some of the
cylinders is working fine and I can get it to shift into gear smoothly
in one direction only either foreword or reverse, and when I try to
adjust for the other gear I lose my adjustment for the opposite.
But wow even having one direction adjusted is great and you almost can't
tell when it goes into gear!
This inability to find a medium shifting range to allow both gears to
engage smoothly seems to be caused by something that my manual doesn't
cover and I wanted to ask here to verify my assumption. I feel I have
too much slop in my neutral position of my transom bracket shifting
cable. I know there is a detent ball in the in the clutch shaft but by
removing the transom bracket shift cable and manually moving the cable
back and forth...it seems to travel too far ( 3/8" either way from
center ) and I can't feel the detent.
Should there be that much play in the cable before the shift arm starts
to move?
Thanks.