[Public-List] stern tube question
George Dinwiddie
gdinwiddie at alberg30.org
Mon Feb 4 15:26:00 PST 2019
Michael,
As I recall,
- I dug out the old dolphinite
- I think I put something on the cutless bearing housing so that the
5200 wouldn't stick to it, but I don't remember what. If you don't do
this, you can heat the base of the cutless bearing housing with a
propane torch if it's stuck to the caulk.
- I screwed the stern tube into the cutless bearing housing.
- I made sure the stuffing box and stuffing box hose were on the
shaft. Or maybe I didn't, and pulled the shaft out to put those things
on later.
- I mounted the cutless bearing housing on the stern over the shaft.
- I put a stick between the shaft and the stern tube to roughly center
the shaft in the stern tube. I don't know why this seemed necessary to
me. It probably isn't.
- I crawled over the engine and squirted mucho 5200 around the stern
tube. In retrospect, the dolphinite might be a better choice, but my
arms wouldn't have been long enough to push that into place, anyway.
- I let that caulk set up for a week or so. It was about a tube of caulk.
- I assembled the stuffing box and hose onto the forward end of the
stern tube.
- I loosened the flange and adjusted the engine alignment.
- I took the cutless bearing housing off, and put it back on with caulk.
- I put the prop back on.
- I launched the boat and discovered I had not sufficiently caulked
the upper bolt. I don't recommend that part.
- I re-hauled the boat, removed the bolt, caulked, and refitted the
bolt. You can skip this if you do it right the first time.
- I relaunched the boat, and celebrated that it wasn't dripping.
- I started the engine, and nervously put it in gear.
- I motored home without having a heart attack.
Believe me, I understand the trepidation about doing this job. It's
really more straightforward than it seems. There are many unnecessary
steps I did that I've left out of my narrative.
For what it's worth, I did all this because I noticed the stern tube had
rotated. The screws of the stuffing box hose clamps were no longer
pointed upwards where I could get a screwdriver on them. I feared that
it would leak and sink the boat.
In hindsight, I think I could have screwed the stern tube fully into the
cutless bearing housing and squirted some caulk around it to tempt it
into not turning. Probably it wasn't likely to turn, but had turned some
time when I was putting the cutless bearing housing on or taking it off.
Now that I know that dolphinite wasn't keeping the water out, I wouldn't
be so worried. I didn't realize that at the time.
- George
On 2/4/19 4:40 PM, Michael Connolly via Public-List wrote:
> David and George,
> I stand corrected. I was missing something. So from your good advice and photo references. I must assume that during fabrication Whitby assembled all together, bolted the cutless bearing housing onto the aft end of keel and then crammed in the Dolfinite around the stern tube.
> Does that make sense? Otherwise how would all this easily line-up with the stern tube fixed into the hull ahead of time?
>
> So with an older boat with a dislodged stern tube it would be best to start the process all over again. That is, remove the stern tube completely, scrape out all the accupucky, then assemble all the new components together with the stern tube slipped over the shaft. Align the engine to the cutlass bearing and then refasten the stern tube in place with new flexible sealant.
> Michael
>
>> On February 4, 2019 at 3:57 PM David Fay <davidfay999 at gmail.com mailto:davidfay999 at gmail.com > wrote:
>>
>>
>> [After writing the note below I saw that George had already replied to Michael and provided much the same information. I'm sending this anyway in case anyone finds it useful.]
>>
>> Hi Michael,
>>
>> Your understanding is not quite correct. The prop shaft needs to be concentric with the stern tube because the cutless bearing and its housing must be concentric with the stern tube (because the housing screws onto the stern tube). If the prop shaft is not concentric with the stern tube before the cutless bearing and housing are screwed on, then the prop shaft will apply sideways pressure to the cutless bearing wearing it out.
>>
>> It's also somewhat misleading to say the stern tube provides "a water tight passage for the prop shaft". Once the boat is in the water, the stern tube is filled with water. The water enters through two holes in the cutless bearing housing, passes through holes drilled through the sides of the cutless bearing by the installer (this step is skipped by some installers), and then travels aft to fill the cutless bearing and cool it down as well as forward to the stuffing box and its packing to keep them cool.
>>
>> Even if the holes are not drilled into the cutless bearing, some sea water will enter the cutless bearing from the aft end because the rubber lining that holds the prop shaft in place is grooved allowing a small amount of water to travel through the bearing, into the stern tube, and on to the stuffing box.
>>
>> A diagram or photos would be helpful here.
>>
>> David
>>
>> > > On Feb 4, 2019, at 10:38 AM, Michael Connolly via Public-List <public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org > 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
>>>
>>> > > > On February 3, 2019 at 5:04 PM Clay Pass via Public-List <public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org > wrote:
>>>>
>>>>
>>>> I think that test assumes that there is not any play in the rubber cutlass
>>>> bearing that might allow the shaft to hang low as it is resting on the
>>>> bearing or it is pushed over to one side or the other because of wear in
>>>> the bearing. I think that if you removed the cutlass bearing and housing
>>>> you should have been able to visibly see shaft move off center in the stern
>>>> tube as it was rotated.
>>>>
>>>> On Fri, Feb 1, 2019 at 10:11 PM Kris Coward via Public-List <
>>>> public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org > wrote:
>>>>
>>>> > > > >
>>>>> > > > >> As a note, my wobble wasn't visible. That said, it was detectable prior
>>>>
>>>> > > > > to removal by uncoupling the shaft from the engine to test the
>>>>> alignment, rotating the shaft by one coupling bolt, testing the
>>>>> alignment again, and seeing that it was different. Once out, it was
>>>>> confirmed by rolling the shaft down a reference flat surface (one of the
>>>>> granite slabs at a machine shop, which are used specifically to make
>>>>> sure that things are really flat, though I've heard that granite
>>>>> countertops and mirrors also work).
>>>>>
>>>>> > > > > > -K
>>>>>>
>>>>>> > > > >
>>>>> > > > > > On Fri, Feb 01, 2019 at 10:01:12AM -0500, David Fay via Public-List wrote:
>>>>>>
>>>>>> > > > > >>> Don,
>>>>>
>>>>> > > > > > >>
>>>>>> >> Thank you so much for your comments. It's not what I wanted to hear but
>>>>>>
>>>>>> >> you've opened my mind to new possibilities.
>>>>>>
>>>>>> > > > > >>> My initial thought was that there couldn't have been much force applied
>>>>>
>>>>> > > > > > >> to the shaft because the wrap didn't stop the engine. Plus I have that
>>>>>>
>>>>>> > > > > flexible coupling, which is supposed to avoid damage in just this kind of
>>>>> situation -- the weak link as you call it. But we'll see. The next step
>>>>> will be to see if the shaft wobbles when I rotate it.
>>>>>
>>>>> > > > > >
>>>>>> > > > > >>> David
>>>>>
>>>>> > > > > > Blue Teal #284
>>>>>>
>>>>>> >>
>>>>>> >>
>>>>>> >>>> On Feb 1, 2019, at 9:39 AM, Don Campbell via Public-List <
>>>>>>
>>>>>> > > > > > > >>>
>>>>>>>
>>>>>>> > > > > > > > public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org > wrote:
>>>>>>>>
>>>>>>>> > > > > > >
>>>>>>> > > > > >
>>>>>> > > > > >>>
>>>>> >>>>>
>>>>> >>>>>
>>>>> >>>>> David:
>>>>> >> You have probably bent the drive shaft with the dockline as I
>>>>> >>
>>>>> >>>>>
>>>>> >>> suspect that is the weakest part of your drivetrain.. If you recall, Kris
>>>>> Coward said he had a bent driveshaft and I have had one as well. The bend
>>>>> in my shaft was about 0.005" and was small enough that the machine shop I
>>>>> took things to managed to work that back to straight with a lathe and some
>>>>> sideways pressure. Stainless is very malleable, and bends easily. I am
>>>>> surprised though that you only have a 7/8" shaft for a diesel. They are
>>>>> usually a full 1" because of the extra torque developed by diesels. It the
>>>>> shaft did not bend, then the coupler probably gave because of that torque
>>>>> or, if that did not fail, a motor mount has bent. You should have that
>>>>> diesel on flex mounts. Whatever has been the resistance with the dockline,
>>>>> it will have been the torque developed by your motor that will have caused
>>>>> the weakest link to fail.
>>>>>
>>>>> >>>
>>>>> >>>>> Don
>>>>> >>
>>>>> >>>>>
>>>>> >>> ---Original Message----- From: David Fay via Public-List
>>>>> Sent: Thursday, January 31, 2019 9:21 PM
>>>>> To: Alberg 30 Public List -- open to all
>>>>> Cc: David Fay
>>>>> Subject: Re: [Public-List] stern tube question
>>>>>
>>>>> > > > > > Michael,
>>>>>>
>>>>>> > > > >
>>>>> > > > > > That's possible of course, but this is not some ancient clunker of an
>>>>>>
>>>>>> > > > >
>>>>> > > > > >
>>>>>> > > > >
>>>>> > > > engine but rather a new Beta Marine diesel installed just five years ago by
>>>>
>>>> > > a highly competent boat restorer (Tim Lackey). I would be very surprised if
>>> a rope wrap could twist the engine around on its engine mounts. But it's
>>> certainly something I will have to look into.
>>>
>>> > > > >>
>>>> >>
>>>> >> David
>>>>
>>>> > > > > Blue Teal #284
>>>>>
>>>>> >>
>>>>>
>>>>> > > > > > On Jan 31, 2019, at 8:30 PM, Michael Grosh via Public-List <
>>>>>>
>>>>>> > > > >
>>>>> > > > public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org mailto:public-list at lists.alberg30.org > wrote:
>>>>
>>>> > >
>>> > > > >>
>>>> >>>>
>>>> >>>>
>>>> >>>> It sounds like the line wrap may have pulled the engine out of
>>>>
>>>> alignment.
>>>>
>>>> > >
>>> > > > >>
>>>> >>
>>>> >> _______________________________________________
>>>>
>>>> > > > > These businesses support your Association:
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>>>>>
>>>>> > > > > >
>>>>>> > > > >
>>>>> > > > _______________________________________________
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>>>>
>>>> > > Kris Coward http://unripe.melon.org/
>>> GPG Fingerprint: 2BF3 957D 310A FEEC 4733 830E 21A4 05C7 1FEB 12B3
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--
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When I remember bygone days George Dinwiddie
I think how evening follows morn; gdinwiddie at alberg30.org
So many I loved were not yet dead, http://www.Alberg30.org
So many I love were not yet born. also see:
'The Middle' by Ogden Nash http://idiacomputing.com
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