1998 8HP two-stroke tiller-handle shifting not very crisp after many years

Serial #0G590511
The engine has served us very well for 22+ years. It has shift/throttle control on the tiller handle.
The last couple of years, it hasn't been shifting as crisply and easily as it did when new. Sometimes
as you turn the twist grip to go into gear, the throttle opens so it is way above idle when it finally goes into gear.
And, you need to return the twist grip to get back down to idle.

There is a long line of components between the twist grip and the actual reverse gear.
I've got a new tiller handle pulley with shift/throttle cables and did some greasing...that is operating very smoothly.
The lower unit is relatively new...the shift shaft goes up and down smoothly.

That leaves the plastic pulleys and gears, horizontal shift shaft, the shift-shaft yoke, and detent spring.
All of these have been greased many times with 2-4-C w/teflon. Would it make sense to
take all of them apart, clean them up, and put it back together with fresh grease?
Should I use a de-greaser? Or, just wipe them clean?

Remove all that GREASE.
I've never seen all that GREASE on a new motor. It will collect dirt
And then it won't work at all.
And don't put grease on the manual pull rope COIL SPRING. Their
Supposed to be completely DRY.

Here is a page out of the Mercury Factory Service Manual.
It shows greasing in 6 places using 2-4-C w/Teflon.
The old grease should certainly be removed....use degreaser or will that damage the plastic parts?

Well, I am revisiting this shifting problem. I almost got to the point where I figured it must be a problem with the lower-unit.
Was eyeing purchasing a new lower-unit for ~$1200. I decided to go to the local Mercury dealer and borrow a bearing-carrier
removal tool ($100 special service tool). With some penetrating oil and an impact wrench, I finally got the bearing-carrier loose. Turns out
everything inside looks ABSOLUTELY FINE! Glad I didn't sink the $1200!

So, back to the parts in the power head. Only thing I've noticed is that the horizontal shift-shaft has a lot of end-to-end play in it.
I have another identical 8 HP that does NOT have that much play. We are talking maybe 3/16 inch on the engine in question.
I'm going to replace the horizontal shift-shaft, the yoke, and the detent spring. We shall see what happens.

Well, I figured it out. A few years back, I had been prying on the detent spring to try
and get the yoke (shift lever...part that the shift-shaft connects to) back on.
I had figured it was just a thin tang and would easily bend. I had to pry hard on it.
It took a slight bend which there should NOT be. It is a very strong spring. Got a new
spring and all is fine. Correct procedure is to loosen the two screws holding the
detent spring to get the yoke back in.