Re: Help with my 1988 150 Mercury Black Max
Depends on the exact LU you have, but essentially you have gotten the shift rod out of place.
On some, if you accidentally pull up on the shift rod, you can drop parts out of place internally. More likely, it's just not in the right place.
If you get your shifter, and the LU in the same gear, ie forward or neutral, then put it back on, it should work in all gears.
I do mine in neutral, and rotate the flywheel to line up the driveshaft splines.
The devil's in the details.
hope it helps
John