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Old 15-02-2012, 22:52   #1
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Exhaust Hose Advice

Hi there my fellow sailors,

a question for ya:

I live in Mexico and it is very difficult to get hoses, especially marine hoses. I needed to replace the hose that goes from the stuffing box to the outside outlet, that exits salt cooling water and exhaust humes and gasses.

Now, the only hose I could find that was strong enough and still flexible enough can hold up to 150 F or 66 C temperature of the exhaust gasses and cooling water. My pretorien is only used for coastal sailing and not long trips. The maximum time the engine will be used is an hour. Can I do safe coastal sailing with this hose?

I have a volvo penta in my sailboat of 45 HP. I hardly bring it up more than 2.000 RPM.

Also, because of the limited length of the hose that was available, I could not connect it in the way the previous hose was connected, which was in a downwards way from the stuffing box over a length of appx. 3 ft and then directly going upwards for appx. 1,5 ft (50 cms) over a beam and down to the outlet. Now the hose goes inmediately in an upwards direction from the stuffing box to a max of appx. 1,5 foot (50cms) in the end and then over the beam down to the outlet. The outlet of the engine towards the stuffing box is appx. 1 foot (35 cms) high. The total length of the exhaust hose from the stuffing box is appx. 7 ft. Can this cause a problem of cooling water flowing back into the engine or is the amount of water that will flow back not enough to go up the 1 foot to the engine?

I am unaware if I have a protection valve that avoids water from flowing back into the engine. I have a volvo penta 1981.

Please advise.
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Old 15-02-2012, 23:28   #2
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Re: Exhaust hose advice

See EXHAUST INSTALLATION

The stuffing box is not part of the exhaust system, so you are confusing us.
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Old 15-02-2012, 23:37   #3
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Re: Exhaust hose advice

OK, my apologies for the confusion, maybe when I describe how things are connected it will give u a better picture:

there is the volvo penta engine, a short hose goes down from the volvo penta engine to the stuffing box with a difference in height of 1 foot

then from the stuffing box, placed on the bottom of the hull, the new hose goes in an appx 20 degrees upwards direction up to a max height of 1,5 foot and then inmediately down to the outlet

now, as I understood the little light brown plastic box between the exhaust hose to the outlet and the hose to the engine is called the stuffing box right?
If not, then I dont know what its called but it is a small light brown plastic box between the exhaust hose

I hope you now understand the situation and I am a little concerned about it so I really appreciate your advice cq. comments
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Old 16-02-2012, 00:22   #4
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Re: Exhaust hose advice

The stuffing box is the unit the shaft goes through before it enters the water. This seals the water from entering the boat while allowing the shaft to turn the wheel. What you are describing that sits flat on the bottom or floor sounds more like a lift muffler usually made out of GRP. A high temperature exhaust hose is attached from the exhaust manifold that has water and exhaust entering. some but not all use GRP pipe and short sections of hi temp hose to get this exhausted from the boat.
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Old 16-02-2012, 06:15   #5
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Re: Exhaust Hose Advice

Quote:
Originally Posted by pretorien View Post
... Now, the only hose I could find that was strong enough and still flexible enough can hold up to 150 F or 66 C temperature of the exhaust gasses and cooling water ...
Greetings and welcome aboard the CF, pretorien.

I wouldn't recommend using 150F/66C rated hoses for a wet exhaust system.

Standard grade marine wet exhaust hose is generally rated to at least 176F (80C) to 212F (100C); whilst the preferred higher quality exhaust hoses maximum continuous temperature is rated up to 250F (121C).
Some high performance silicone rubber exhaust hoses are rated to 300 to 500 F.
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Old 16-02-2012, 08:21   #6
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Re: Exhaust Hose Advice

I think by stuffing box, you mean water muffler. Is that the case? It can be a black round or rectangular unit, often black or brown.
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Old 16-02-2012, 11:41   #7
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Re: Exhaust Hose Advice

OK, by stuffing box you mean the water lift muffler, or what Yanmar calls the waterlock in their diagram. As you can see in the linked diagram in my previous post, the top of the waterlock should be no less than 10 inches below the mixing elbow which comes out of the engine, which it seems to be in your case.

The Yanmar diagram also says that the top of the gooseneck (which in your case is the top of the loop of hose) should be no less than 350mm above the waterline (more is better). They also recommend that the hose go up at least 150mm from the exhaust outlet. The higest part is what is important--if your previous hose went down from the waterlock and up, but your new hose just goes up, its OK as long as it goes at least as far UP.

The hose from the exhaust elbow (engine) to the waterlock is critical to be high temperature, as a temporary loss of cooling water can get it really hot. From the waterlock to the transom is not as critical--you can probably get by with 150 degree hose there for a while, and upgrade it when you can get the proper materials.
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Old 16-02-2012, 12:05   #8
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Re: Exhaust Hose Advice

Not sure where you are in Mexico, but just to the south here in Guatemala we have good availability of hoses. If you plan to come this way then you can probably find what you need here.
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Old 16-02-2012, 17:10   #9
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Re: Exhaust Hose Advice

Thank you all for your help and especially Don Radcliff I think you got a very good pic of the situation. And you all were right, the box that I called stuffing box (as somebody in my surroundings pointed it out) is in fact the waterlock. I found a pic on the yanmar page which is practically the same.

So it seems for the moment the hose that goes from the waterlock to the outlet is all right. It goes up from the on the bottom connected waterlock in a 25 angle to a max height of I would say between 1,5 and 2 ft. and then straight down to the outlet, which is appx. half a foot above water level.

I was a little concerned that the water that would remain in the hose after shutting of the engine, would slide back into the waterlock to the engine, although it would have to go up 1 ft in a 40 angle towards the engine.
But if this will do for a couple of months of local coastal cruising, then I am happy. I think ordering the hose I need would take appx. 4 to 6 weeks.

Thank you for your help everyone and if you have any more comments/advice then please feel free.
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