Shift shaft won't align after water impeller change on Merc 225 Optimax with Torque M

[morgmach]

2016 Mercury Optimax with Torque Master lower unit.
I put in a new water impeller and when reinstalling the unit the shift shaft won't align correctly with the Lower Unit (LU) splines that attach to the LU gearbox.
I initially had the unit in forward gear to avoid this and put things back together. I went fine, however I was unable to shift into reverse (motor was off for all of this). The shift lever at the drivers console was so stiff it would not go into Reverse and I didn't want to force it and break something. I did have to slightly move the shift shaft when installing but it was minor, however I thought maybe that caused the unit to miss align.
I dropped the LU again to see what was wrong, however everything looked good. I took someones advice and moved the shift lever at console to neutral and then put pliers on LU gear spline and moved it to neutral as well. I go to reinstall and I can't get the splines to line up with the LU gearbox aluminum "tube" that extends up to the shift shaft.
The drive shaft is all the way in and engaged at the top, I have that down to a science now. It is more difficult with the LU in neutral but it still goes in.
Any help is greatly appreciated.

Model Number 1226P73BD
Serial Number 2B123665
225 PXST2

Thank you.

[Savage]

Get a second set of hands to align the shift shaft, as you push the lower unit up.

[Jtreed99]

You probably had it dead nuts correct the 1st time but you can’t shift without the prop spinning.

[morgmach]

Thank you. Could you explain that why that is please? I appreciate your helping.

[morgmach]

Savage, I had a helper but I just learned that if someone slightly turns the prop clockwise while slowly putting it in forward gear the dogs will align better with the "splines". I'll try that when I get home tonight. I also didn't know you can't put it in reverse without the prop moving manually (someone turning it slowly counter clockwise), thus I may have had it correct before dropping it again. Urgg.... live and learn. Thank you for helping sir.

[EuropeanAM]

I MUCH prefer NEUTRAL and NEUTRAL as it is a relatively fixed position. "In Gear" leaves a variable of several degrees rotation.

Check the shift slide on the side of the engine. The cable end-pin should be "dead-nuts centered" between the two small screws that retain the shift position switch.

Have a friend turn the flywheel with a 15/16" socket and ratchet (clockwise) to assist in indexing the driveshaft... and reach between the swivel shaft and the driveshaft housing to manipulate the shift shaft into position.

[morgmach]

Fixed! Thank you ALL for your help.
I used Neutral and Neutral to fix mine. The wife slowly put boat into forward gear at the console while I spun the prop shaft slowly, it clicked right in.
Again, no reverse, but went to lake and went into forward and neutral several times and reverse finally synced up and all is well. Except my aching back, knees and thighs, but it's fixed thank Goodness.
Many thank yous to you gents for helping me out.