Re: Prop Shaft Squeak

ngtnewington Newington
 

Hi James,

1.  If the boat is ashore I would check that the shaft is true. You would need to pull it and take it to a machine shop.

2. I would check the engine alignment again. It is not easy to get spot on. One of the tricks I have learned is to decouple the shaft from the transmission and centre it within the stern tube. Then align the engine to the shaft.

On some systems the shaft is floating around and can be moved a lot as there is no bearing at the engine end of the stern tube. This would be the case with a modern drip free lip seal style stern gland. From the photo I think this is what you have. If there is shaft wiggle then make up a nylon bearing that slots into the stern tube at the front end, this involves removing the shaft seal, and sliding the nylon bearing over the shaft and into the stern tube. So there is a cutlass bearing aft and another nylon temporary bearing forward. This then centres the shaft spot on within the stern tube. With the shaft centred you then align the engine to it. It needs to be spot on. Then obviously remove the temporary nylon bearing, and put back the shaft seal.

The problem is that  it is much easier to do out of the water but the hull may take up a slightly different shape ashore, although if it has been carefully chocked and is nice and level a solid hull like a Maramu will probably not move much.

If in the water, I have used a  greased tape or plastic wrapped around the shaft and pushed into the cutlass bearing to reduce the flow. This works quite well, but water leaking into the boat adds a bit of stress.

There are other techniques, but this is my preferred.

Nick

S/Y Amelia AML 54-019
Kilada Greece.




On 24 Nov 2019, at 03:35, James Lochhead <j_lochhead@...> wrote:

HI,

The attached photo is of the stuffing box and where the shaft on my maramu exits the boat.  Is the circled part another bearing that is glassed into the hull?

We have a "sqeak" or hum when the prop shaft is spinning at certain revs (both with engine and when sailing and free spinning) that we have not been able to diagnose.

The problem started following the failure of our engine mounts.  The engine mounts have been replaced and the cutless bearing was replaced at next haul out, however a squeak has remained on our last short cruise before hauling out again.  I have checked the engine alignment, the stuffing was replaced, but the squeak remained.

We will be back on the boat again in the new year and would like to eliminate the cause for this before going back in the water and if this is a bearing then possibly order one now.

--

James
Maramu #147 (1984) <Shaft photo.pdf>

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