Propeller Shaft

9/28/2010

I started to look at the propeller shaft, stern tube, packing gland, etc. At the inboard end of the stern tube, I removed the packing gland (see below).


I then tried removing the inboard support but it appears to be welded to the stern tube, which is tightly fitted to the dead wood. (fitting shown below)


So it’s very unlikely that I would be able to remove the stern tube. I then switched my attention to the outboard end. After some finagling, I realized that the stern tube is threaded on the outboard end, with a large locking ring to hold the rear support against the deadwood.


The locking ring was designed to be removed with a spanner, but I was able to remove it with judicious use of a hammer and drift. The ring has a threaded hole for a large set screw, but the hole in the ring no longer matches the hole in the stern tube and the screw is missing. Removing the support revealed that the wood behind it is in bad shape.


The cutlass bearing also has a set screw, which I removed. I then tried to remove the cutlass bearing with an improvised bearing puller.



The puller consists of a threaded rod with an 1.25" washer and nut at one end to seat against the inboard end of the bearing and a much larger washer and nut at the other end to seat against a short section of pipe which seats against the outboard end of the stern tube. The ID of the pipe is large enough to provide clearance for the bearing. Unfortunately, the bearing is in too tight. I’ll have to saw it out.

10/11/2010

My research on removing cutlass bearings suggests cutting them out. The bearing is a bronze tube 1.5” OD with about a 3/16” wall – 4” long. I bought a Lennox hand saw that takes a Sawsall blade.


This cuts easily through the soft bronze. The problem is judging the depth of cut – you want to avoid cutting into the stern tube. You can see it ok on the outboard end but not the other end. In the future, I suggest making a depth gage to check this, because it caused me a lot of trouble.

After cutting a slot at the bottom, I tried to collapse the tube with a hammer and drift – it don’t go well. The pic below shows the bearing still in the stern tube.


The bonze is soft but the thick wall resists bending – it just sort of smashes and chips off. I got nowhere. I tried to hammer a drift into the set screw hole, but this didn’t accomplish anything. On Carson’s advice, I tried cutting another slot in the top of the tube. In theory, this should allow the tube to collapse without having to bend. The problem is that I couldn’t judge the depth of the saw cut inboard. And now with 2 slots, a depth gage wouldn’t help even if I had one. At this point, I decided to cut another slot about ¼” to the right of the first one. Then with a lathe tool bit and a hammer, I was able to peel the bronze away between the two slots. This process put some gouges in the stern tube, but created enough space so that I could start collapsing the tube (combination drifts and lathe tool). Once started, I could wedge a big screwdriver between the stern tube and bearing tube and twist with a wrench – further collapsing the bearing.

Of course my slots weren’t deep enough towards the inboard end, so I could only collapse about ½ the bearing. But this was enough to break it loose. I was then able to drive in out from inside the boat with a nut & washer on the end of a threaded rod. Took quite a bit of pounding to get it out.


I then use a circular wire brush (a 2” that I ground down to 1.5” diam) to clean out the corrosion products.


Note, I just attached it to a drill extension and plunged it in and out by hand. The wire brush would remove too much material if turned in a drill.

On close inspection, I could see that the stern tube had numerous dings from previous bearing removal and the new ones that I added.


I think it will be ok, however. I also noticed that the stern tube has a shoulder where the bearing seats. So the stern tube itself has an ID of about 1.25” with the outboard end machined to 1.5” for a length of 4”. This explains why I couldn’t fit a 1.5” washer in from the inboard end.

I tried removing the prop from the shaft, but my small arbor press won’t budge it. I want to remove it and apply anti-gall to the contact surfaces. In that way, if I ever have to change the prop, maybe I can do it more easily.

10/22/2010 (or there abouts)

Took the propeller shaft to Carson's shop, where an haudraulic press is waiting. At about 6-8 tons, the shaft released from the prop - sounded like a rifle shot. Inspection showed the the shaft is taper on the end with a keyway. The key, however, has long since corroded away.