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I've sprung a leak
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Justin Butler
145 Posts
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7th June 2018 - 12:35 am
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So I went to check the boat today, having noticed a decreasing relationship between how much rain we've he'd and how much water is in the boat... I have a leak. There is water coming in where the stern tube passes through the hull. It is typical that it's something hard to get at. The stern tube is glassed in along its exposed length which strikes me as a bit unusual, perhaps a previous repair.

I know this isn't something that a gentleman should say to a lady, and certainly not to other gentlemen, but could we compare stern tubes? is yours glassed glassed right up to the stern gland or is the metal tube exposed? Time for an electric bilge pump I think

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Stephen Moorey
275 Posts
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7th June 2018 - 10:16 pm
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Hi Justin,

what type of seal have you got. ?. Ive got two pumps installed, both have packed up this week.  My stern tube is fully glassed in.  surely its the seal that's leaking, the stern tube does not act as a seal .  deep seal seals can be adjusted and a stuffing box seal usually has a greaser to seal the joint.

 

 stephen

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Stephen Moorey
275 Posts
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7th June 2018 - 10:51 pm
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Hi Justin,

Ive read your post again.  From what I can remember both Twisters ive had and the stearn tubes were exposed inside the boat.  The first Twister had a deep sea seal on it and the rubber boot attached to it.    

 

stephen 

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Justin Butler
145 Posts
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7th June 2018 - 11:58 pm
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Hi Stephen,

The stern gland isn't leaking, I repacked it before I launched and I've checked it. I can see water trickling in where the stern tube passes through the hull (about 2 feet aft of the stern gland). The stern tube is glassed in from that point,all the way forward to the first floor, then comes the floor and then the stern gland... Surpringly hard to describe..

Regards,

Justin

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John Tetlow
249 Posts
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8th June 2018 - 2:36 pm
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Tammie20Norie20Cockpit20hatches20DSC00865.jpgImage Enlarger

 

You may be able to see from this photo that the stern tube on "Tammie Norie" is exposed from where it enters the hull up to the stern gland.

My advice would be to put the boat ashore and then remove the outboard bearing, clean it up and re-bed it on the sterpost with a suitable mastic.

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Justin Butler
145 Posts
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8th June 2018 - 4:08 pm
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Thanks John, that's a big help.

For reasons a can't explain mine has been glassed in. And I suspect you're dead right about the cause of the leak. It can only be one of two things, either a hole worn through the stern tube ( extremely unlikely) or the mastic seal between the cutlass bearing and the stern tube. If that was leaking it would allow water to creep up the outside of the Stern tube. Its not a serious leak, I've got an auto bilge pump that I'll install, even without that it would take a couple of weeks before the floor boards were awash. I'll keep an eye on it and overhaul the cutlass bearing when she comes out in three  months.

Thanks for the input Stephen and John,

Justin

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John Tetlow
249 Posts
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8th June 2018 - 7:38 pm
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I should have said there are three places that need sealing :

1.  The threads where the sternbearing screws into the stern tube. I used a thread sealing compound, probaby a Loctite product.

2.  Ditto for the inboard bearing.

3.  The flange of the sternbearing where it bolts onto the 'sternpost'. I think I used some non-setting variety of Sikaflex there.

I wouldn't be surprised if the extra fibreglassing around your sterntube is a previous owner's attempt to stop a leak without really understanding where it was coming from.

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Peter Mulville
251 Posts
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10th June 2018 - 11:40 am
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John Tetlow keeps an immaculate Twister and offers most sound advice. I sure hope it works. I think John's comment about the fibreglass around the sterntube is a worry.

The bad news is that about 15 years ago I replaced VIVEZA's stern gear when we sprang a leak. The problem was that the inner end of the stern tube, where it is threaded and screws in the inboard bearing, had been subject to some electrolytic corrosion such that some of the thread was missing. 

The stern tube is not glassed over. The outboard bearing bolts through the hull. It's a joy to tighten the lower bolt. The inboard bearing is bolted to a glassed in floor...as in Tamie Norie. I confess that there was a leak last year from this. I found that I had not sealed the thread in the sterntube where it screws into the inboard bearing and stuffing box. 

The sealant I use is called Heldite. It's used in submarines I'm told. It's easily found on the web. It's truly perfect for the job. It was recommended by the excellent T Norris. Marine engineers and suppliers of my replacement sterngear. See:  http://www.tnorrismarine.co.uk/

If you want to talk through removing the sterngear happy to do so. 

Peter

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Justin Butler
145 Posts
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9
3rd October 2018 - 6:50 pm
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Hi All, quick update. I have identified the source of the leak. The boat has been lifted out. If I took hold of the floor that the sterngland/inboard  bearing is bolted to (with the prop shaft in place,but uncoupled from the engine), I found that I could lift and drop the whole assembly by about 3/4 of an inch. This includes the floor! Which has come unstuck.

I initially thought that the stern tube was broken. Happily it's not. The entire assembly is now in my garage and I'm going to email T Norris tonight for parts and advice.

Only about 6 inches of the stern tube is contained within the hull, and at that end, the stern gear was only held in place by the two cutlass bearing carrier bolts..the Stern tube itself had about 3mm of slop in every direction. There's no doubt in my mind why it was leaking now.

I plan to reinstall the Stern tube with epoxy around it, then glass in the floor again (properly this time). With new bearings all round and then sealed up properly. That should sort it.

Justin,

Roquetta

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Stephen Moorey
275 Posts
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3rd October 2018 - 11:12 pm
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Justin,

You've had another busy week.  Those through hull fittings looked hard work !!. not sure ill remove all the ones ive got fitted.  Great you've identified the leak problem, like the new access hatch.

Stephen

Helix 

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