Need help putting on lower unit - Mercruiser Pre Alpha

Hi guys, newbie here.

My buddy has a boat with a pre-alpha (R?) outdrive I believe. His boat wasn't going into gear so we were told to make sure that everything looked good in the lower unit. I have absolutely never worked on a boat outdrive before but I have a good amount of auto experience (not sure that matters here).

Anyway we took the lower unit off and it came off really nicely. However since the boat wouldn’t go into gear we took it off in neutral. We were told to make sure the shifter cable was locking in so we put it in forward gear. Then we couldn’t get the lower unit back on – because the upper unit was in forward and the lower was in neutral. We were able to lock the prop CCW on the lower unit so I think we’re good. We haven’t put it back on yet.

But quick question – when the boat is in gear everything should lock up. However there is a brass tube with a cotter pin through it on the upper unit. It looks to be connected to the shift cable. When putting everything back together it’s loose and moves up and down and turns. Is that supposed to be locked when the boat is in FWD gear too? It slides over the smaller set of splines towards the back of the lower unit. What is that brass tubes purpose - if any?

We’re pretty lost here so any help would be appreciated. We still don’t know if the thing goes into gear now so I’d love to hear some ideas and troubleshooting on what it could be.

Thanks for the help, and sorry for my lack of boat knowledge. These outdrives are really funky.

It slides over the smaller set of splines towards the back of the lower unit. What is that brass tubes purpose - if any?

Pay close attention to the second word there "SLIDES"
With the upper shoe in full fwd at the control box, and the lower units splined shaft turned fully clockwise until the prop is locked CCW (fwd). raise the drive up .
To get the driveshaft splines to mate, turn the prop CCW about an inch, unit should go up. put the front nut on with 2 turns.
Now place the lower brass shoe on the lower splined shaft so its in a straight line.
PLACE not force it .start the 2 side nuts and tighten making sure THE LOWER BRASS SHOE STILL SLIDES and goes into the upper shoe without binding.

Bt Doctur said:

It slides over the smaller set of splines towards the back of the lower unit. What is that brass tubes purpose - if any?

Pay close attention to the second word there "SLIDES"
With the upper shoe in full fwd at the control box, and the lower units splined shaft turned fully clockwise until the prop is locked CCW (fwd). raise the drive up .
To get the driveshaft splines to mate, turn the prop CCW about an inch, unit should go up. put the front nut on with 2 turns.
Now place the lower brass shoe on the lower splined shaft so its in a straight line.
PLACE not force it .start the 2 side nuts and tighten making sure THE LOWER BRASS SHOE STILL SLIDES and goes into the upper shoe without binding.

Click to expand...

Thanks for the reply! So it's supposed to twist and move while in gear so that it can line up with the splines?

What would cause the boat not to go into gear then? Is there a shifter cable adjustment point we don't know about?

looking at the pic N is to your right, R is fully turned to the right

Okay so we were able to get it engaged in gear but we've gotten it this far and it literally won't move anymore. We have tried turning the prop a little bit to help line up the splines but nothing is happening. It's so close but won't go that last half inch.

What could be binding up on this or stopping us from getting it back together?

you are lining up the copper water tube into the plastic guide tube and a lubricating the rubber sleeve in the pump top cover?
to have it that close you should have the brass shoe installed on the lower spline and it should be in a straight line to meet the upper shoe

this drive is in neutral, fwd would be in a straight line facing you and hopefully to rememberd to install the SS washer on the lower splined shaft

Bt Doctur said:

this drive is in neutral, fwd would be in a straight line facing you and hopefully to rememberd to install the SS washer on the lower splined shaft

Click to expand...

Where exactly is this in reference to the lower unit? Is this exposed or covered by anything?

As far as lining it up the copper sleeve is on the smaller spine. I'm not sure if he lubricated the water tube or not. You can literally see the screws trying to poke through the top it's very frustrating to be so close!

with the drive raised the brass shoe is visable

Same issue happened to me today ,when replacing my impaller ,as usually I get impatient and rushed , wouldn’t go into gear , after installing lower unit back . , looked back at my pictures before and after impaller assembly as I always to with my work . Missed a oil seal and the metal washer . Kicking myself for this