[Public-List] stern tube question

Michael Connolly crufone at comcast.net
Mon Feb 4 12:49:53 PST 2019

I have also heard the term "shaft log". Is this just another name for the stuffing box or does it refer to the stern tube?

> On February 4, 2019 at 3:34 PM George Dinwiddie via Public-List <public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org > wrote:
>     Michael,
>     The stern tube does not keep the water out. It allows the stuffing box
>     to keep the water out at a more convenient location than glassed into
>     the aft end of the bilge.
>     While the stern tube is sealed by the stuffing box one one end, it's
>     threaded into the cutless bearing housing on the other. The cutless
>     bearing housing should be caulked to not allow water to reach the
>     outside of the stern tube. The inside is wet with water that comes up
>     the grooves of the cutless bearing, lubricating it and keeping it cool
>     while the shaft is rotating.
>     The engine and cutless bearing need to be aligned pretty closely to
>     reduce friction, which both wears the cutless bearing and torques the
>     shaft. If there's enough friction, the shaft becomes a pretzel.
>     The stern tube needs to be aligned well enough to clear the shaft, but
>     also let the stuffing box ride on the shaft without wiggling the tube
>     around. Fortunately both the original dolphinite and the 5200 that's
>     often used in rework are flexible enough to accommodate any misalignment
>     as you're installing things. Then the cutless bearing housing holds the
>     stern tube in that alignment.
>     - George [who's more familiar with this construction than I'd like]
>     On 2/4/19 10:38 AM, Michael Connolly via Public-List wrote:
>         > > Hello all,
> >         It is my understanding that the stern tube was secured into the boat to provide a water tight passage for the prop shaft. There are no bearings in the stern tube on our boats. There needs to be enough clearance so the shaft does not rub against the tube, wearing a hole in it to cause a leak for sea water into the boat. No need for the tube to be absolutely concentric with the shaft as long as there is clearance for the length of the shaft inside the tube.
> >         Michael
> > 
> >     >     --
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