Mercury 40-HP Swivel Tube Repair

[gubernaculum]

I have reduced every 2 x 4 block I had on hand to splinters with my 5-lbs hand sledge, so I am here for help if anybody has been through this:

The swivel tube on my Mercury 40-HP FOURSTROKE 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 picture).

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 and steering arm up and out. No luck there either.

Schematics

IMG_2997.JPG (93.72 KiB) Viewed 5255 times

Broken part

IMG_2999.JPG (112.26 KiB) Viewed 5255 times

Can't pound it down, can't pound it up.

IMG_3001.JPG (127.04 KiB) Viewed 5255 times

I was able to pound the whole assembly up about 5-mm. I was able to pound the splined end of the swivel tube down about 1-mm inside the steering arm, but no farther. WHAT AM I MISSING HERE?

[Jefecinco]

Does the shop manual suggest any solution?

Is it possible the surface rust and probable pitting is interfering with the removal? Have you tried all the potions and lotions used for penetration and lubrication of tightly fitting parts?

I would clean off all the rust and even use some abrasive to bring the shaft back to it's normal size, Spray the area liberally with a strong penetrant/lubricant, let it soak for several hours then give it another try. If the cold approach fails I would hit the shaft with heat from a propane torch and give it another go while it is hot. A last ditch try could include dry ice, bottled co2 or an ice-salt-acetone liquid applied to the assembly. Portable hydraulic presses are sometimes available at rental outlets. One might get the job done if you can rig a safe purchase for the press. Finally, I'd consider a repair shop.

[gubernaculum]

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. Still not exactly sure why it wouldn't go up.



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.

Thanks for the suggestions/encouragement. Now I just have to put all this crap back together!!!

[jimh]

This situation reminds me of the old joke:

Q: How many therapists does it take to change a lightbulb?

A: It only takes one, but the lightbulb has to really want to change.

I think of that old joke whenever some mechanical assembly I am working on refuses to come apart. I figure I just don't really want to get it apart enough.