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Old 10-09-2013, 08:54 PM   #1
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Monk 36 - leaky stern tube

I own a 1984 single screw Monk 36 with a leaky stainless stern tube. I would very much appreciate any suggestions or experiences dealing with this problem. Water fills the hollow keel and then finds various ways to come into the boat. Have tried patching areas where water is entering from the keel - but the water keeps finding a new point of entry. I have heard that replacement of the tube is extremely difficult. Thanks for any help!
Charles
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Old 10-09-2013, 09:06 PM   #2
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I too have heard they are difficulty to deal with...the most common remedy SUGGESTED , though I haven't heard of one being done, is to coat the tube with epoxy or slide a new thin glass lined covered with epoxy into it if there's enough clearance.
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Old 10-09-2013, 09:06 PM   #3
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Patching a stern tube

Re-repairing bad patch job where keel and cutlass bearing housing mount

You may be able to glean some information from these two threads. Welcome to the forum.
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Old 10-09-2013, 10:23 PM   #4
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I had that problem w a FG tube.

Needed to replace the stern tube.

Perhaps you should try that stuff that can be applied to wet surfaces. Can't remember it's name.

You could haul the boat and drain the keel ... get things dried out and repair w common epoxy.

Failing the epoxy you could probably install a FG stern tube. I bought mine in Bellingham WA and could act as middle man but I'll bet the drying and epoxy sealing will do the trick.
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Old 10-10-2013, 12:08 PM   #5
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Thanks for the comments and the links (which were very interesting). Unfortunately, it would be difficult to open up the keel cover to expose the stern tube because of all the cabinet work above it. The boat is presently hauled - and we are trying to get a plan. The yard is concerned that trying to remove and replace the tube could be extremely problematic and there are several web posts that agree & say it was very difficult and not something they would want to repeat.

Probably the best route would be a sleeve (if there's enough clearance) or some type of epoxy to fill the holes in the tube - plus continue to try and make the false bottom(above the hollow keel) as water-tight as possible.
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Old 10-10-2013, 01:46 PM   #6
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The sleeve idea has merit I think as long as the tube is big enough.

But since you have it out of the water epoxy should seal it up if you can get at the bottom above the keel. Keel water should drain enough to dry the hull above the keel. I think that epoxy I mentioned before is "Splash Guard" .. but not sure.

Having a flooded keel will lower CG.
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Old 10-10-2013, 02:22 PM   #7
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Unfortunately, there is little room for a sleeve. Shaft is 1 3/4" and ID of shaft tube only about 1 7/8"! (2" OD shaft tube).

When an attempt to put the boat back in the water yesterday was made - water came out of a hole in a small bulkhead in front of the engine. The bulkhead had been glassed when the boat was built - and the glass had delammed a bit - allowing water from the keel to push up between the wood bulkhead and the fiberglass bulkhead covering and out the hole!

So - now were thinking of re-glossing that bulkhead to keep the water from entering the boat. This will be the third time we've tried to stop the water from entering the boat from the hollow keel. Each leak allowed water to enter at about a rate of a few gallons every 5 minutes or so - so the leaks have been substantial.
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Old 10-10-2013, 03:03 PM   #8
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Have been told that paraffin can be used to fill shaft tube. Not to sure how that would be done or how it would work. just another idea.
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Old 10-10-2013, 06:03 PM   #9
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I would sleeve the tube and then turn down the existing shaft so it fits. A good quality SS that is 1 ľĒ should still has plenty of strength.
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Old 10-10-2013, 09:22 PM   #10
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Charles,

I had the same problem in our previous boat. The generator was out due to stringer replacement which is an entirley different story. I cut out the false floor over the V where the shaft ran then dug out the disgusting, stinking, saturated foam that filled the cavity. Once that was done I pulled the shaft, and pluged the opening at the rudder. Then made up a fitting so I could put air pressure on the tube to be sure it was the culprit. It was. If you use air pressure 4 lbs is plenty.

From there it was sazall time. I cut the tabbing and the big chunk of solid glass at the stuffing box. It was much easier than I thought it would be. I think it was also leaking where the aft part of the tube went through the hull because once I made the mentioned cuts it just lifted out.

The next step was a tube which I found after a google search at Nor Easter Yachts Nor' Easter Yachts, Inc. - Custom Fiberglass Manufacturing - Milford, CT in Milford, CT less than a hour away. I had the yard glass it in as I wanted it to be in perfect alignment. Seaport Marine in Mystic, CT did a great job for me.

Photo 221 is the false floor cut away, foam (Did I say it was putrid?) dug out, shaft ready to remove. If you look close, you can see where the tabbing has been cut with the sawzall.

220 shows the whole shaft including the corroded fitting the stuffing box attaches to. That solid chunk the stuffing box fitting had to be removed as well.

230 Everything cut away and ready for the new tube. Not a good shot it was much cleaner than it looks.

228 The old tube. The leak is in the red circle.

226 fitting the stuffing box attached to.

Sorry to say I can not find a shot of the finished project. Will post if I do.

Good Luck,

Rob
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Old 10-10-2013, 09:29 PM   #11
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Better when photos are attached.

Rob
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Old 10-14-2013, 04:18 PM   #12
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Thanks for the additional suggestions - and all those great pictures!! The pictures are very useful - and really do a good job of showing how your stern tube was installed. I'll bet my installation is similar.

What was the boat model? Was it a trawler built n Taiwan in the 80's - when it seems a lot of these boats with the stainless tubes were constructed.

My Monk 36 has a lot of woodwork above where he stern tube is located - but, I guess the woodwork could be removed to allow access. In your pictures, It also looks like the stainless tube was left bare - except for the two places where it was attached to the hull - is that correct?

I'm curious - how long did it take you to get the old tube out - once you had it exposed as in the picture? Any special tools that were particularly helpful?

The paraffin idea is interesting - but I would think it would only be a short term solution. I also spoke to the yard about using a sleeve & then trucking the diameter of the shaft. The shaft is 12' and they thought that we might run into a problem with a thinner shaft starting to oscillate in the tube and create a lot of clatter.

Thanks again for all your help!!!
Charles
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Old 10-14-2013, 07:40 PM   #13
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One other thing you may like to check are the engine supports.

FWIW, a previous boat of mine had the same symptoms as yours. It turned out the stringers supporting the rear engine bearers had been compressed(rotted) over the years and the resultant angle of the drive shaft coupling forced the shaft and tube to break the water tight seal flooding the boat.

Probably not your issue but worth a quick check of the rear engine mounts.
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Old 10-14-2013, 09:34 PM   #14
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Charles,

The boat was built by Sunk Yong Marine in Korea. A 1979 37' Sedan. I did not have a stainless tube, it was fiberglass and looked like it was made by wraping glass around a pipe. The one I replaced it with was much higher quality.

Once the tube was exposed it only took about 45 minutes. It was just a matter of cutting the tabbing and the solid glass at the stuffing box. I did it all with a sawzall. What really suprised me was how easily the aft end of the tube where it went through the hull came out. I think that joint had failed or was ready to.
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Old 11-09-2013, 11:30 AM   #15
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It might not be the tube

Had the same problem on my MT, turned out to be a poorly seated aft coupling.

I'd pull everything apart (or pay someone to do that) before concluding it's the tube. I thought the same thing - replace the tube - when it all came apart it was simply a matter of putting it back together properly.
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Old 11-09-2013, 03:10 PM   #16
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Thanks for those suggestions and Great ideas. The boat is currently hauled awaiting a decision on what to do. The shaft has been removed, along with the stern cutlass bearing - and visually the tube looks OK. however, the next step will be to cut an access hole in the false bottom above the keel - so we can visually look at the stainless stern tube and do a water pressure test so can verify the location of the leak. If the tube is bad, will see if there is an acceptable PVC of fiberglass sleeve than can be inserted (current stainless tube ID is 2.25", and prop shaft is 1.75" OD). Otherwise am considering a complete replacement of the stainless tube with a fiberglass unit.

But, we will first verify the stainless tube is bad!
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Old 11-09-2013, 07:19 PM   #17
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I had a leakey tube on MT. Pulled the cutless bearing and.the tube. Had a new one machined from bronze. No big deal
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Old 11-09-2013, 08:42 PM   #18
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What size was your tube? Was the original tube stainless?
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Old 11-09-2013, 08:53 PM   #19
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Quote:
Originally Posted by motion30 View Post
I had a leakey tube on MT. Pulled the cutless bearing and.the tube. Had a new one machined from bronze. No big deal
Are you talking about the shaft that connects the inner and outer cutlass bearing holders that can be upwards of 10 feet long in a single engine trawler that is glassed/cemented in?
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Old 11-10-2013, 08:38 PM   #20
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Quote:
Originally Posted by charles hicks View Post
What size was your tube? Was the original tube stainless?
It.was brass, they seem to last 25 to 30 years. Bronze. Ss or plastic. All will out last u
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