'05 Mercury 40hp 4stroke: Can't remove swivel tube (w/ pics)

I have reduced every 2x4 block I had on hand to splinters with my 5lb hand sledge, so I am here for help if anybody has been through this:

The swivel tube on my 40hp mercury 4stroke efi corroded away, and finally failed catastrophically with a minor grounding at planing speed on a sandbar. It snapped - you can see where in the photo below.

I removed the lower unit.
Removed the power head.
Removed the upper motor mounts once the power head was off, and then was able to remove the adapter plate and driveshaft housing, exposing the top of the swivel tube. (See pics).

From there, I just can't beat the swivel tube out of the steering arm in order to replace the swivel tube.

The swivel tube has male splines, going up into the female splines of the steering arm. The swivel tube is supposed to drop out from the bottom. I beat on it with a socket, and was able to budge it down a bit, but no farther.

Since the swivel tube is broken in half, I tried to beat the whole swivel tube + steering arm up and out. No luck there either.

above: schemaitics


above: broken part


above: can't pound it down, can't pound it up. I was able to pound the whole assembly up about 5mm. I was able to pound the splined end of the swivel tube down about 1mm inside the steering arm, but no farther.



WHAT AM I MISSING HERE?

Good news - got it out. Here was the trick:

I pounded it up from the bottom until the steering arm would clear the stops and spin 360 degrees. Then I put a block of wood under the side of the steering arm and pounded it upwards. The steering arm actually came up and off of the tube. Then I was able to pound the tube down and out.



Here's the failed part. As you can see the tube wall corroded so badly it is visibly thinner/ "necked down" at the bottom part once it is no longer protected inside the swivel bracket. Seems like a pretty terrible materials choice they made for this part, which is hard to inspect, hard to clean, and causes catastrophic failure when it lets go. The tube sheared off immediately above where the cast piece (part of the lower motor mount) ends inside the tube. This is a salt water boat but low hours and stored inside and cleaned obsessively since we got it 5 years ago. Prior to that it had 5-6 years on a boat lift in the Keys.

now I just have to put all this crap back together!!!