[Public-List] Stern tube

Clay Pass clay.q.pass at gmail.com
Sat Jun 13 19:42:43 PDT 2020

I don't think you need tape on the threads because a leak there would only
travel to the inside of the tube and be stopped by the stuffing box.  As
long as you caulk the tube/housing/hull interface there should be no leaks
to the interior.  Am I wrong?

Clay Pass
#449 Seeing Deep

On Sat, Jun 13, 2020 at 2:42 AM Gerard Kuperus via Public-List <
public-list at lists.alberg30.org> wrote:

> Here is a report on the haul out to fix the leaking stern tube.
> I brought the boat over to the boat yard on Tuesday afternoon and was told
> that I would be second in line the next morning. I did a bit of prep work,
> such as unbolting the engine and figured I would have more prep time in the
> morning. When I arrived on Wednesday morning the crane guy greets my
> happily. It turns out the other people still didn’t show. The boat is on
> the dry a half hour later. After a quick power wash (bottom paint looks
> great!) I am disassembling things. One of the issues on my boat is that
> there is not enough clearance between the prop and the rudder to take off
> the prop, so I have to lift the engine and get it forward a couple of
> inches. After a few attempts I got it off the mounts and create enough
> clearance so that I am able to take everything apart. For some reason the
> coupler only moved a little bit, but I found that I was able to remove the
> shaft from the inside. By lunch time I was in pretty good shape. I took
> everything home to clean up. The tube was in overall good shape, with just
> a tiny bit of corrosion where it must have been touching the stuffing box.
> The shaft also has a bit of wear close to the stuffing box.
> It was actually incredibly easy to take the tube out and as I cleaned out
> the inside I found out why: the thiokol, dolphinite, or whatever stuff was
> used, was very brittle and I pulled out a huge wedge of the stuff that had
> been embedded against the deadwood (to fix a leak one wonders?). I decided
> to fiberglass the tube in place on the inside, which I did after cleaning
> everything out, sanding, reassembling everything and putting the engine
> back in place (so that everything aligns). I managed to get the first layer
> of mat and epoxy in by 10 pm. A way too long day, especially in 85 degrees!
> The next morning I took out the stern tube again (as I turn the fitting it
> popped right out of the fresh epoxy). One slight problem: I was unable to
> get the fitting from the stern tube. When I epoxied it up, it must have
> glued together. I started to caulk things up with 4200. There is a lot of
> space in there! When it started to fill up I also caulked up the bronze
> fitting and moved it into place and caulked up the bolts and tightened
> those up again. On the inside I could see how far the 4200 had travelled.
> At the front end I drilled holes on both sides in the fresh epoxy to add
> more there. Not surprisingly there was bit of a hole at the bottom (almost
> unreachable and invisible). After removing the excess caulking I added a
> layer of epoxy filler (epoxy with adhesive powde)r, followed by another
> layer of mat and epoxy. Looking good! After lunch I added a layer of 4200
> (just in case) around the epoxy. Probably overkill, but I might as well
> finish that second (!) cartridge.
> After checking the engine alignment I launched again by the end of the
> day. I did a quick check – everything dry. Motored back to the marina.
> Checked one more time and I see … WATER! Oh no! I am dumbstruck and my
> exhaustion after two days of hard work and a few weeks of planning is
> getting me down. Where does it come from? It turns out to be the rudder
> post. Thank goodness! I will tighten it up soon, but for the time being I
> dried everything and placed a sponge below the post. I checked one more
> time after dinner, and the next day: all good!
> Besides the huge wedge of the grey caulking I found one other oddity: the
> stern tube and stuffing box are both 1 5/8” OD. I double and triple
> checked, but there was no way in the world a 1.5 inch hose would fit in
> that. It is an odd size.
> My main purpose here was, of course to fix the leak, but I did not give
> myself a lot of time. I knew I should have taken another day. I got it done
> in two days as I really wanted to get the boat and myself out of the yard
> again. This is the only DIY facility open at this time (they actually never
> closed they told me and had the busiest season ever because people had time
> to work on their boats) and while the people there are great, it also a
> harbor full of liveaboards who are literally one step away from
> homelessness. Social distancing and face masks are optional at best and
> while I normally love to tell people that this is not a Triton (as they
> typically assume here in the SF Bay Area, where a lot of Tritons were
> built) but another Alberg design, it becomes a bit less attractive when you
> have to keep trying to physically distance yourself…
> In any case, while the repair should last me for a while, I also think
> that sometime in the future I will replace the bronze tube with a
> fiberglass one, epoxy that in on both sides and also replace the shaft.
> With sour ribs and stomach, I don't really want to think about that, but if
> I had more time on the hard that is what I would do (I will not complain
> about the fact that we have no off season here).
> Thank you again for all the excellent advice I received! I am very happy I
> got this fixed and instead of figuring it out on the spot, I knew exactly
> what to expect. There are always some surprises but you helped me to limit
> them to just a few.
> Gerard
> ________________________________
> From: David Fay <davidfay999 at gmail.com>
> Sent: Sunday, June 7, 2020 11:08 AM
> To: Gerard Kuperus <gkuperus at hotmail.com>
> Cc: Alberg 30 Public List -- open to all <public-list at lists.alberg30.org>
> Subject: Re: [Public-List] Stern tube
> Hi Gerard,
> It did not occur to me that the threads needed tape or caulk (mine just
> had grease) but it makes sense. You really don't want water to escape
> through that joint.
> But that wouldn't have solved my problem. My problem was that a big chunk
> of threads were missing from the end of the stern tube because someone at
> some time had sawn into them with a hack saw blade while trying to remove a
> cutless bearing. (A standard way to remove a recalcitrant cutless bearing
> is to cut it in several places from the inside with a hacksaw blade and
> then collapse it on itself.) There was enough of a hole in the threads on
> the end of the stern tube that water was able to escape the tube.
> So why hadn't the stern tube been leaking ever since the hacksaw episode?
> I'm not sure but I think that when I was removing the bearing housing, I
> rotated the stern tube a bit and that may have sprung the leak.
> I bought my fiberglass stern tube from Spartan Marine because I keep my
> boat at Derecktor Robinhood Marina and Spartan is right there. They also
> had a cutless bearing that fit the tube they had and installed it for me
> (did a nice job too). I don't remember the exact length of the tube but it
> was around 11 inches. You should measure your boat for the length and
> diameter of the tube you need. Its length will depend first on how far it
> sticks out behind the hull, which depends on how much room you have in
> front of your prop and how much room you want to leave for prop shaft
> zincs. It will also depend on how far it penetrates inside the boat, which
> in turn depends on where it needs to attach to your stuffing box hose.
> The outside diameter of the stern tube will be determined by the hole in
> your hull that the bearing housing occupied -- in other words, the stern
> tube outside diameter will be the same as the outside diameter of the
> forward end of the bearing housing, the part that the stern tube screws in
> to (wish I had a picture). The inside diameter of the stern tube will be
> determined by the diameter of your prop shaft (usually 7/8") and how much
> clearance you need around it (the inside diameter of your old stern tube
> would be about right).
> In all of this, I am assuming that you will replace both the stern tube
> and the bearing housing with a single fiberglass stern tube, like I did.
> There may be a way to replace just the stern tube with a fiberglass one and
> retain the bearing housing, but I don't know how you would mate the two.
> In any event, it's not necesssary to get a fiberglass stern tube from
> Spartan Marine -- in fact, I'm not even sure they offer them in their
> catalogue. But there are plenty of other companies out there that do sell
> them. This may be helpful also: a step-by-step description of a stern tube
> replacement on a Pearson Triton by Tim Lackey with lots of good pictures:
> https://www.lackeysailing.com/archived/daysailor/rebuilding/systems/sterntube.htm
> About glassing in the stern tube: that's exactly what I did (and what Tim
> Lackey did), even though some people warn against it (because it's too
> permanent, I suppose). If you do that, just make extra sure that you
> properly align the stern tube with the engine because it's going to be
> really hard to change the alignment of the stern tube if you get it wrong.
> David
> On Jun 7, 2020, at 1:22 PM, Gerard Kuperus <gkuperus at hotmail.com<mailto:
> gkuperus at hotmail.com>> wrote:
> David,
> Can you explain what the defect on the threaded joint was? Worn out, or?
> It is my understanding that the threads need tape and caulk and it is here
> where I expect I might have made a mistake when reinstalling. I put
> caulking on there, I remember, but no tape, and I also remember some going
> back and forth in order to line things up, which actually might have
> squeezed the caulk out.
> Maybe that is wishful thinking... If I do end up replacing the tube, where
> did you buy it and do you have the dimensions? I might order it now, and
> have it handy in case I need to replace it.
> Lastly, I am wondering why the stern tube is not glassed in place.
> Wouldn't that solve some of these issues?
> All the best,
> Gerard
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