Prop Shaft Bearings

[sy_doinit]

The shaft log/stern tube/thru hull. I had a hard time figuring out what it was called and that seems to get me the most results.
Yes, we viewed the shaft in the water. Its very murky and polluted here. Could a bit from the stern tube have deteriorated and got jammed in the tube? The motor mounts don't look great but the engine seems aligned. I'll check the .005" in the morning. We think maybe the PSS and stern tube dried out as it appears that the shaft that is rusted was sitting partially in water. We were gone for ten months and the boat sat in this filthy water, there was a flood and there are strong currents. There is a build up of clay at the waterline and it feels very dense. It builds up really fast. Unless something is stuck in the stern tube, i assume the noise is from misalignment though it was perfect when we left.

[deblen]

Some links that may help diagnose

Shaft Bearings | Cruising World

[deblen]

https://www.youtube.com/watch?v=3UvyF-NRooQ

[deblen]

https://www.youtube.com/watch?v=YTQ997vAq08

[Cheechako]

Is it possible that there is so much growth on your prop or shaft that is causing this?
The other thing that occurs is when a boat sits for a long time, and the prop shaft never turns, the stale water in the packing or cutlass becomes oxygen depleted. This attacks stainless steel like the shaft. It can corrode very fast, creating a very rough, almost worm holed surface. This then tears up the packing and cutlass when you run it.
I've seen this happen in a matter of months.
I seriously doubt the boat mis aligned it self sitting in the water.

[deblen]

Here is how most boats with PSS dripless Inside Packing Gland would be rigged.

The PSS rubber boot would be hose clamped to a Stern Tube/Shaft Tube

The Stern Tube is a hollow pipe,slightly larger than the Propellor Shaft.
The Stern Tube goes from the inside of boat,where PSS rubber boot is clamped to it,to the outside back end of the keel.There MAY be a bronze Shaft Log bolted to back of keel to accept the back end of this tube.There MAY be O-ring seals in the Shaft Log to seal the Stern Tube.

The Stern Tube normally stops at back end of keel.
The Prop. Shaft continues on toward the Propeller.
In your case,you have a Strut coming down from hull,which the Shaft passes through. There will be a Cutless type bearing in this Strut,to support the Shaft. It is lubricated by the surrounding water passing through the grooves in the Cutless Bearing.

There MAY be another Cutless Bearing mounted in the Shaft Log,in which case the Log would be called a Stern Bearing. This extra Cutlass is not necessary on a short sailboat shaft,but OK if it is there.

I suspect you have dirt/mud/etc that has travelled up the space between the Prop.Shaft & the Stern Tube,possibly as far as the PSS Seal.

[deblen]

Shaft Logs On Buck Algonquin


You are going to have to remove clamps from PSS rubber boot,Slide boot toward engine, & flush the dirt out of Stern Tube. Your boat will not sink-see video

/ Len

[CarlF]

Looking back at your first post, you said it runs fine in reverse. Really fine? No unusual noise? How about high speed reverse?

This would shorten the list a lot. Obviously a transmission problem could do this but it's hard to see how rust, growth, PSS, or cutlass bearing wear could cause extreme noise in forward and be completely absent in reverse. Does the shaft move aft noticeably when going to reverse. Is the shaft harder to turn by hand one way or the other? How about turning each way by hand disconnected?

I looked up your tidal range - 2M. Is there a seawall or wharf where you could dry out? Tow the boat there with the dinghy. That's what we did before travel lifts. You could easily inspect the stern tube. You could also pull the shaft and polish the rusted area. But I still don't understand how those two things could be terrible in forward but not there in reverse.

I also agree with Deblen that an easy experiment is to slide the PSS forward for a moment and see if a lot of crud flushes into the bilge from the stern tube. Have a 12" flexible stick to slide in around the shaft to feel for anything. Inspect the shaft that you can see there.

Carl

[deblen]

Some useful How To videos at this link

www.marinehowto.com

[sy_doinit]

shaft log/ stern tube/. thru hull. the part between the shaft seal and the shaft going into the water.
today we went down again and it appears the shaft is rusted. i'd assume the shaft seal dried out while we were away. it looks like the shaft vas sitting in water by the corrosion marks. we are in very polluted water at the mouth of a river from a manmade lake upstream that travels through many villages. we also used the amp meter and saw that there is a current coming through the shaft of like 60 millawatts. Hoping that the shaft is grounded through the engine.
Anyhoo, the motor mounts look decent though should also be replaced. however the engine alignment is good. the shaft is disconnected from the gearbox and a real challenge to spin. Is it possible the cutlass bearing could cause the tension and tighten up around the shaft. I find it hard to understand how it goes ok in reverse and not forward. Our plan now is so reconnect the shaft to the gearbox and run the engine in reverse for a while hoping that whatever is in there breaks loose. There is no option at this point to haul out here or anywhere close. The tides aren't big enough to do the work that way. The water is very murky and doing these things underwater when they've never been done by us is not tempting. Do you think the running in reverse may help or are we wasting our time?

[sy_doinit]

Originally Posted by Cheechako

Is it possible that there is so much growth on your prop or shaft that is causing this?
The other thing that occurs is when a boat sits for a long time, and the prop shaft never turns, the stale water in the packing or cutlass becomes oxygen depleted. This attacks stainless steel like the shaft. It can corrode very fast, creating a very rough, almost worm holed surface. This then tears up the packing and cutlass when you run it.
I've seen this happen in a matter of months.
I seriously doubt the boat mis aligned it self sitting in the water.

I think you nailed it. Any suggestions? Happy to replace everything but need to get to that spot first. How fast does it tear those things up?

[DeepFrz]

I suggest you haul out and find out what the real problem is. We can sit here and play 20 questions but you will never be sure unless you haul out and to it right.

[sy_doinit]

Originally Posted by deblen

Shaft Logs On Buck Algonquin


You are going to have to remove clamps from PSS rubber boot,Slide boot toward engine, & flush the dirt out of Stern Tube. Your boat will not sink-see video

/ Len

i don't see a video. i'm a little affraid of sinking the boat but am pretty confident it wont' happen.

[sy_doinit]

Originally Posted by DeepFrz

I suggest you haul out and find out what the real problem is. We can sit here and play 20 questions but you will never be sure unless you haul out and to it right.

If you can tell me where that convenient place is i'd be happy to do that but it's 150 miles down the coast into the wind and current. Or I could go 900 miles back across the south china sea to the tip of Borneo, winds might be better for that trip. Just getting out of the bay here with the currents will be a challenge. I think Cheechako has it right w ith the corrosion. Just trying to figure out if i can get it good enough to get out of here and to the haul out down south. and "to it right".

[sy_doinit]

Originally Posted by CarlF

Looking back at your first post, you said it runs fine in reverse. Really fine? No unusual noise? How about high speed reverse?

This would shorten the list a lot. Obviously a transmission problem could do this but it's hard to see how rust, growth, PSS, or cutlass bearing wear could cause extreme noise in forward and be completely absent in reverse. Does the shaft move aft noticeably when going to reverse. Is the shaft harder to turn by hand one way or the other? How about turning each way by hand disconnected?

I looked up your tidal range - 2M. Is there a seawall or wharf where you could dry out? Tow the boat there with the dinghy. That's what we did before travel lifts. You could easily inspect the stern tube. You could also pull the shaft and polish the rusted area. But I still don't understand how those two things could be terrible in forward but not there in reverse.

I also agree with Deblen that an easy experiment is to slide the PSS forward for a moment and see if a lot of crud flushes into the bilge from the stern tube. Have a 12" flexible stick to slide in around the shaft to feel for anything. Inspect the shaft that you can see there.

Carl

I didn't have it at high rpm's in either gear so i can't really answer that. It's hard to turn on both directions, even when it's disconnected. I will look into places to work with the tides but I don't really see that being an option. The bottom is soft mud and silt here. I'll consult the tide chart.
In pulling the PSS off a little, we have been letting water in but don't see anyhting too strange in there, just murky water. Not seeing any bits of anything. It's rusted for sure and I think Cheechakoo is on to something. I just want to know if we can remedy this to get to the haul out yard.