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Old 09-12-2012, 01:10 AM   #1
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Have Air/Exhaust Escaping

Help. Quite new in experience & have got air/exhaust coming through the drive shaft outlet through the hull in starboard engine on my Marine Trader 39. Has anybody any ideas what is causing this & possible remedies. Thanks
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Old 09-12-2012, 06:34 AM   #2
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Sounds like the engine room does not have sufficient air intakes and your engines are lowering the pressure in the engine space.

This CAN NOT be solved with an intake blower as engine fumes may get pushed thru the entire vessel.

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Old 09-12-2012, 07:48 AM   #3
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... have got air/exhaust coming through the drive shaft outlet through the hull in starboard engine on my Marine Trader 39.
??? Does that mean someone saw bubbles coming from the around the shaft where leaves the hull? Is air leaking out past the cutless bearing?
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Old 09-12-2012, 07:56 AM   #4
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That is exactly what is happening. Since I posted here on the Forum I have checked & all is dry in the bilges. The problem doesn't occur at idle only when engine reaches 800/1000rpm.
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Old 09-12-2012, 07:59 AM   #5
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It sounds like your seawater pump is sucking air someplace and some of it is being pushed out with the bearing cooling/lube water. You can confirm this by closing the valve to the stuffing box if you have one. If not then just disconnect the water line and run it into a bucket to see if you have a bunch of air in it.

If you do have air then start looking for a leaking gasket on the sea strainer or hoses on the suction side of the raw water pump.

If you don't have any air in the suction then this is a great mystery.
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Old 09-12-2012, 05:55 PM   #6
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It sounds like your seawater pump is sucking air someplace and some of it is being pushed out with the bearing cooling/lube water. You can confirm this by closing the valve to the stuffing box if you have one. If not then just disconnect the water line and run it into a bucket to see if you have a bunch of air in it.

If you do have air then start looking for a leaking gasket on the sea strainer or hoses on the suction side of the raw water pump.

If you don't have any air in the suction then this is a great mystery.
Was thinking exactly the same thing but that would have to be a lot of air to notice it...way more than I would think would wind up in that line from the entire cooling system with no other symptoms.

All I can say is WOW!

But your troubleshooting ideas are where I would head too....
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Old 09-12-2012, 06:59 PM   #7
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Was thinking exactly the same thing but that would have to be a lot of air to notice it...

Yeah, that and to create enough suction to overcome the head due to draft, there must be something restricting the seawater inlet. Either something in the strainer itself or the hull valve or intake grid if there is one.
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Old 09-13-2012, 05:35 AM   #8
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Thanks Guys for all your ideas & input. Have investigated along the lines of your explanations as to what it could be, but alas have found no diagnosis as to the cause. However on starting the engine this morning to check for any leaks or sucking of air, the problem seems to have gone away. This in its self worries me because I am sure it will reoccur at sometime. But all I can do at this stage is keep an eye on it until such time as I get the boat lifted during winter lay up & investigate further. Thanks again.
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Old 09-13-2012, 06:43 AM   #9
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As long as you don't have any engine or exhaust cooling problems and there is some water going to the cutless bearings you really don't need to worry much about it.

Does this happen only when the shaft is turning?
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Old 09-13-2012, 08:04 AM   #10
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Hi Rick
No it has been apparent when the engine is running. Have checked the propellor & there is no tightness. It can be turned quite easily by hand, with the same effort as the port engine. As far as I can see the shaft isn't running hot, so am happy that water is getting to the bearing.
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Old 09-13-2012, 10:00 AM   #11
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Well, that kind of points toward something in the raw water circuit either sucking air or leaking exhaust into the system but I can't see the backpressure being high enough to allow exhaust gas to overcome circ water pressure. Does the flow of bubbles change with engine rpm?

Weird.
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Old 09-13-2012, 10:08 AM   #12
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Yes. When engine revs increased the bubbles increased. But as I said, for some reason it has stopped doing it now!!!
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Old 09-15-2012, 02:58 PM   #13
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Here is a theory that may or may not hold air or water With or without a vented loop your raw water system may drain down and trap air some of which goes out the exhaust and some through the cooling line to the shaft log. Possibly you have a loose hose connection somewhere letting air in or maybe even your exhaust elbow is clogged putting more pressure on the shaft log system. Alternatively it could be something that has been going on occasionally prior just escaping your notice.

I have heard of shaft logs that have a bearing in them being overpressurized by the cooling water flow causing the packing gland to leak inboard. I don't know if your Marine Trader has that type system. If the exhaust elbow is clogged I would think you could tell that by measuring its temperature and the exhaust plumbing. Typically those parts will run between 100 and 130 degress F.
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Old 10-18-2012, 03:44 PM   #14
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I have now reached my winter's lay up location in Ragusa Sicily & the problem of bubbles emitting from the inner cutlass bearing has raised it's head again. More worrying is the fact that I am getting more water than I should be in the previously quite dry bilges. The bilge pump is going off every 12 hours. Soon to be going home, & plan to leave the boat in the water so it is very much a concern.
Now my very limited kinowledge says to me that if air is bubbling out of said cutlass bearing, water will be getting in when engine not running. Now with my lack of basic knowledge is there any one here on the forum that could walk me through the process of how to tighten the stern gland. Incidently the bubbles are there when the engine is started & the shaft not turning.
Thanks very much for your help
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Old 10-18-2012, 04:05 PM   #15
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Greetings,
Mr. Ian. Try this...
Re-Packing A Traditional Stuffing Box Photo Gallery by Compass Marine at pbase.com
Hope it helps...
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Old 10-18-2012, 06:46 PM   #16
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Ian, are you certain that the sea water is leaking into the bilge through the stern gland? Best to double check so that you "don't go fixin' something that ain't broke".

There are many different types of stern gland. If you can post a picture of yours, forum members can probably talk you through the packing procedure - at least enough to stop it dripping while you park the boat up for the winter.
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Old 10-18-2012, 09:09 PM   #17
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Our boat sometimes puts out air bubbles that come to the surface alongside the hull even with the shaft tunnel exits. Our shaft logs do not drip when the shafts are not turning (actually, they rarely drip when they are turning). In looking at the little clear debris filters that are in the raw water pickoff line from the heat exchanger that connects to the shaft log one can see agitation bubbles in the water swirling through the filter. It is these bubbles that are being pumped to the shaft log and out the shaft tunnel.

In other words, it's no big deal.

Our bilge is essentially dry although over time it gets some rainwater in it from the lazarette and also the very slow drips from the shaft logs when the boat is underway. So we vacuum it out every four or five months--- there will be perhaps a half inch of water at the lowest point.

So I agree with Mike. It may very well be that the bubbles are just the nature of of the beast. Sources of salt water in the bilge can be varied. Ones I can think of offhand are:

1. The normal drip from the shaft log when the boat is underway. (Ideally the log shouldn't drip when the shaft is not turning. Adjusting the packing gland is real easy--- lots of descriptions in the archives of this forum.)

2. A leak in the (or an) engine's raw water cooling system. This can be a worn seal in the pump, a seeping hose connection, worn gasket under the cover of a sea strainer, a leaking heat exchanger, etc. This same applies to a raw water cooled generator.

3. A seeping seacock. There are lots of different kinds of seacocks. Our 1970s vintage seacocks are big, bronze, and the fit of the rotating cone in the seacock body can be adjusted by an adjustment and jam nut arrangement similar to a packing gland. Tighten the cone too much and the seacock will be very hard to operate but it won't leak. Adjust the fit too loose and it will be real easy to operate but it will seep water. What you want is the cone to be a tight enough fit not to leak water but not so tight that it's difficult to operate. Like a packing gland, it's a trial and error deal.

4. Leaking wet-exhaust hose. Either from a not-tight-enough connection to a muffler or through-hull exhaust fitting or a bad spot in the hose.

5. Leaking rudder gland.

6. Leaking intake water connection to a salt water toilet.

7. Leaking connection to a salt water washdown pump.

There are probably other potential salt water leak sources but that's what I can come up with now.
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Old 10-18-2012, 09:31 PM   #18
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I have now reached my winter's lay up location in Ragusa Sicily
---------------------------------------
Hey Ian
You made it to Italy finally? If you get a chance maybe you could tell us about cruising the Mediterranean Sea. I'll be in Valencia in September - October 2013, but leaving the boat home.
Larry B
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Old 10-19-2012, 01:25 AM   #19
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the bubbles are there when the engine is started & the shaft not turning.
That seems to confirm earlier wise opinion the problem comes from a raw water feed to the gland, rather than the gland itself. Can you work back, starting from the connection at the gland?
Those excellent pics RTF posted are most informative. On an IG36 with twins you rely on feel as much as sight (see recent thread under Halvorsen) as regards glands. BruceK
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Old 10-19-2012, 03:04 AM   #20
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Hi Edelweis. Yes we have had one great year. I have compiled quite a comprehensive diary type blog. Would you like me to send you copies
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