heavy wear on prop shaft

alan006

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I saw severe wear on a propeller shaft, but the wear is not even all the way round the shaft but all on one side. Is this likely to be caused by engine misalingement or would that cause wear evenly round the shaft. I've seen worn shafts before but not unevenly worn shafts. Any ideas as to what might have caused this?
 

Kawasaki

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Whereabouts is the worn area?
At the inboard end or at the aft end where the shaft runs through its bearing?
I am in the middle of replacing My shaft, sterntube and all that goes with it.
Wear is usually found at the gland end but as you mention generally uniform.
If there is an alignement problem wear on one side will occur.
There is usually a white metal insert in the stuffing box too. this will show an irregular wear pattern also if alignement is out.
Alignement probs can occur if the engine is out of line due to poor condition of the engine mountings.
If You can give details of the arrangement of the prop shaft and how it is supprted externally.
Ie, is there a "P" bracket for support etc.
What Make Model is the Craft concerned?
Bit more info and I can supply the answers I reckon.
For the last 9 months I have been scratching My head trying to cure a problem stern gland.
Now I am renewing everything aft of the Gearbox!
Think I can write a Thesis on Glands, Stern Tubes, Cutlass bearings Props and Propellors, stuffing boxes , shaft logs etc etc etc!
Bent shaft will cause it as said but I don,t think an unbalanced prop will without summat else being wrong.
K
 

alan006

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The wear is just aft of the cutlass bearing. It is a big bronze shaft about 2.5 inches diameter on a heavy displacement wooden boat. The prop looked ok with no damage to the blades so hopefully its not out of balance. The shaft comes out of the cutlass bearing and the prop is only about 3 or 4 inches away, so it would take a bit of doing to bend it. There was no sign of anything having been caught round the prop or shaft.
I think I'll check the engine mounts.
 

fisherman

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Is this the first time you've looked at it? Could be a previous owner has overended the shaft: don't see how you would get wear outside the cutless, except by getting something pretty hard round the shaft and running for a good while.
 

Kawasaki

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So there is no "P" bracket.
So that rules that out!
Most props are Stainless, however on a shaft that size it is obviously a biggish displacement vessel.
Is the cutlass bearing log all nice and tight , is there any movement there?
Could be if the mounting bolts that are there to stop "twisting" are not "home" properly.
The stern tube could be damaged.
Unlikely but it does happen.
They suffer from electrolysis and can deteriate around the area the tube fits into the cutlass log.
If all is OK at the cutlass end it would point most definately to engine mounting alignement.
Normally however, that would show at the inboard end also.
There would be a stern gland seal prob too if the eng was out of line I would have thought.
Has the stern gland benn behaving itself?
 

Kawasaki

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As Fisherman says it is unusual to get wear outside the cutlass bearing.
Unless the log has come loose as mentioned.
Wear like you mention is usually due to summat being wrapped around the shaft for some time.
Do you know if a rope cutter has been fixed at all?
The Spur type have bearings that can wear.
It is unusual for those things to wear the shaft though.
If it possible I would be inclined to remove the prop and draw the shaft out to inspect thoroughly.
B%%er I know but You do have a strange symptom unless there has been summat rubbing on it externally.
 

alan006

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I suppose that with shaft misalignment the stern gland would need much more regular tightening up to avoid leaks as the packing would wear at a quicker rate. As far as I know the stern gland has not needed more attention than normal.
 
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