flexible wet exhaust pipe

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shufti

shufti

Senior Member
Joined
Dec 3, 2013
Messages
199
Location
Australia
Vessel Name
Wine Down
Vessel Make
Riviera 35' FB
Hi All,

The stainless exhaust pipe from the riser to the muffler has developed some rust and pinholes have started to occur. I'm considering switching to a flexible hose product rather than having new stainless pipe fabricated.

Can anyone offer any advice on doing this? Seems all the flexible pipe available is only rated to +100C and I assume temps would be higher than this as the pipe is situated just aft of the turbo. The motor is a Volvo TAMD41A.

Just started my search today so any and all advice/warnings etc are welcome.

Thanks.
 
Measure the temp with a heat gun under 10 min of full load.
 
It sounds as if you are considering the use of rubber wet exhaust hose in the very hot dry exhaust flow directly downstream of the turbo. I think that would be a really bad idea. Flexible metal exhaust hose might work for a while. Can you post a picture?
 
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Let's step back and make sure we are all talking about the same thing.

In a typical installation the exhaust from the turbo goes up in a fabricated stainless steel "riser" and then bends down to an "injection elbow" or "mixer" where sea water is introduced into the exhaust stream to cool it. After that Trident or similar exhaust hose is used to go to the muffler.

So if you are talking about the "riser" then it has to be fabricated from stainless steel pipe- usually schedule 10 with a double wall mixer with holes for the raw water to be injected into the gas stream.

If you are talking about after the mixer then rubber hose can be used as the exhaust gas is cooled in the mixer sufficiently for rubber. If you are concerned about temps then use blue silicone hose as it is good for several hundred degrees F.

But rubber hose can't be bent significantly. There is one common and maybe another uncommon solution if you need to bend more.

The common solution is to use fiberglass elbows such as made by Centek, either 45 or 90 degrees to go where you need to go and rubber hose before and after the elbow.

The uncommon solution is to use a braided flexible stainless steel hose. I have never seen it in the large diameters needed for a trawler exhaust system as I suspect it isn't any more flexible than rubber at those sizes.

David
 
Thanks for the input all. Ok - here's a diagram of the system:

25658.jpg


As you can see - the riser (or elbow) -Part #20 - sits right on the turbo. That is where the water is injected. My rusted exhaust pipe is part #24. Well, not exactly as it's been custom-made by PO. It goes to the muffler, then out the back.

Attached (crappy - sorry) pics show where I'd cut the existing pipe (yellow lines) - then use the flexible pipe (clamped onto the two ends). So yes - it would be in the wet part of the system.

Reason I'm considering NOT just having a new SS pipe fabricated is that the fabricator I spoke to estimed 4-5hrs work ($75/hr) + materials. I doubt I'd get out of it for under $500.
 

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I agree it should not be a problem. You could also change the stainless bends for fiberglass elbows and have no more pin holes in the future.
 
If it worked there would be examples, I have never seen or heard of it.
 
rochepoint said:
I agree it should not be a problem. You could also change the stainless bends for fiberglass elbows and have no more pin holes in the future.
Click to expand...

That is what I would do. Replace part 24 with Trident exhaust hose and a couple of Centek 45 deg elbows. You could use a "hump hose" at one or both of the joints. These allow for a bit of misalignment.

David
 
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Mule said:
If it worked there would be examples, I have never seen or heard of it.
Click to expand...

If you're talking about using hose and fiberglass elbows instead of the SS pipe, it works and it's very common. In fact you're more likely to that than SS pipe.
 
You might consider using Trident Blue Corra-Sil Marine Wet Exhaust & Water Hose (SAE J2006) #252v which is very flexible and minimizes transmitted vibration between the riser and the muffler. It is so flexible that you should be able to eliminate the 45 elbow at the muffler.

At the riser, you could use a Trident Silicone Wet Exhaust Elbow to make the sharp turn back toward the muffler. Use a short piece of fiberglass tubing for the coupler and high quality SS T-clamps, especially on the riser since it looks like it is only wide enough for a single clamp.

The use of silicone components results in much longer service life and higher operating temperatures in the event of a raw water pump failure. The Blue Very High Temp silicone is rated at 350F, 100F higher than normal exhaust hose.

I just finished a similar project and was amazed at how much vibration the corrugated silicone hose and elbows provide. Caution, $$$$$$ alert though! :thumb:

Larry
M/V Boomarang
 
I stand corrected. It is being done.
 
LarryM said:
Caution, $$$$$$ alert though! :thumb:

Larry
M/V Boomarang
Click to expand...

Holy bloody nightmare. You're not joking are you.

Anyone care to recommend a good supplier that will post international?
 
Bevel cut and glass fiberglass tube to get what you need to fit. Join to mixer and to muffler with six inch sleeves of softwall rubber exhaust hose. Lowest dollar option and still good engineering.
 
Ski in NC said:
Bevel cut and glass fiberglass tube to get what you need to fit. Join to mixer and to muffler with six inch sleeves of softwall rubber exhaust hose. Lowest dollar option and still good engineering.
Click to expand...

Or, if vibration control is an issue, you can use EPDM rubber or silicone hump hoses instead of the straight sleeves. Much, much cheaper than what I proposed before. And, like Ski suggested, still good engineering.

I believe either solution will be much better than the stainless tubing.
 
if you dont want a fabrication job, cut the existing pipe where you wish & replace with hose or similar, several different makes available, here are two with distributors in oz
Trident Marine: Wet Exhaust Hosehttp://www.tridentmarine.com/stage/wetexhaust.htm
http://www.seastarsolutions.com/products/hose/wet-exhaust/
the slicone smooth stuff gives better flow than the rubber corrugated stuff but more $, you choose. the rubber stuff works ok for me (shieldsaust C) but I dont have tight bends
you can surely salvage joining pieces / bends out of your existing pipe if you cant run hose for the whole length ??
 
shufti said:
Holy bloody nightmare. You're not joking are you.

Anyone care to recommend a good supplier that will post international?
Click to expand...

Yea, breathtaking isn't it? :eek:

Looks like you might be able to get similar Purosil products in Australia here. They will certainly be more affordable without shipping, duty etc.
 
I'm familiar with the Trident 252V hose that has been recommended. It really is great hose. If my memory is correct it can be had in 3, 6, 12 and 60 foot lengths.
I also know a Trident distributor with great prices who ships to Oz, but the forum rules prevent me from saying who it is.
 
LarryM said:
Yea, breathtaking isn't it? :eek:

Each of my boats have excellent exhaust elbows.....however someday....
Please post a general price range for this hi dollar stuff, you have my curiosity up. Thanks...:confused:
Click to expand...
 
Ski in NC said:
Bevel cut and glass fiberglass tube to get what you need to fit. Join to mixer and to muffler with six inch sleeves of softwall rubber exhaust hose. Lowest dollar option and still good engineering.
Click to expand...

Totally agreed. Epoxy the cut pieces together to hold them in place, clean up the inside, then several wraps of resin-soaked fiberglass tape around the joint.
 
it's still relatively easy to burn through the blue silicon hose.... the 454 on the assistance towboat tried it for 2 seasons and it burned through when the sea water plugged and some throttle was used.

It's good ....but far from VERY high heat resistance...then again I have burned through the fiberglass tubes also...:eek:
 
psneeld said:
it's still relatively easy to burn through the blue silicon hose.... the 454 on the assistance towboat tried it for 2 seasons and it burned through when the sea water plugged and some throttle was used.

It's good ....but far from VERY high heat resistance...then again I have burned through the fiberglass tubes also...:eek:
Click to expand...

Yea, I know the feeling. We once burned through some blue VHT hump hoses on a Donzi, it happened in about 15 seconds when we picked up a plastic bag. We switched to red VHT which is rated at 500F, but it doesn't stand up long to raw, un-cooled exhaust gas! I've seen burnt fiberglass tubes too, on an old Cape Dory sailboat with a little 2-cyl Volvo diesel. It melted the muffler too! It doesn't matter how big or small the engine is, without cooling water, things change mighty fast. Scary stuff . . . even when you try to do everything right..:D
 
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LarryM said:
Yea, I know the feeling. We once burned through some blue VHT hump hoses on a Donzi, it happened in about 15 seconds when we picked up a plastic bag. We switched to red VHT which is rated at 500F, but it doesn't stand up long to raw, un-cooled exhaust gas! I've seen burnt fiberglass tubes too, on an old Cape Dory sailboat with a little 2-cyl Volvo diesel. It melted the muffler too! It doesn't matter how big or small the engine is, without cooling water, things change mighty fast. Scary stuff . . . even when you try to do everything right..:D
Click to expand...

Good examples of the best not really being good enough and the cheap working fine till things go wrong.

Always a crapshoot where to spend your money...:thumb:
 
shufti said:
Attached (crappy - sorry) pics show where I'd cut the existing pipe (yellow lines) - then use the flexible pipe (clamped onto the two ends). So yes - it would be in the wet part of the system.
.
Click to expand...

I'd get rid of all the stainless steel (not try and use the elbows) and just use hose, and if needed fiberglass elbow/s then you can forget the whole thing without thinking that the elbows are going next.
A cooling water flow alarm is a must for me...
 
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Brooksie said:
I'd get rid of all the stainless steel (not try and use the elbows) and just use hose, and if needed fiberglass elbow/s then you can forget the whole thing without thinking that the elbows are going next.
A cooling water flow alarm is a must for me...
Click to expand...

In all cases where I have burned hoses, the engine coolant never got warm...doesn't take much water flow on a 454.

The obvious best sensor in my cases would be an exhaust temp sensor.

I have a water flow sensor on the Trawler's Lehman but I still get nervous about downstream issues like when my oil cooler fell apart on the towboat...flow sensor would have been normal as I'm filling my bilge, but the exhaust would be skyrocketing.
 
psneeld said:
In all cases where I have burned hoses, the engine coolant never got warm...doesn't take much water flow on a 454.

The obvious best sensor in my cases would be an exhaust temp sensor.

I have a water flow sensor on the Trawler's Lehman but I still get nervous about downstream issues like when my oil cooler fell apart on the towboat...flow sensor would have been normal as I'm filling my bilge, but the exhaust would be skyrocketing.
Click to expand...

You are right, you can fry your exhaust b/4 your coolant temp gauge even moves but I am talking about raw water flow sensors.

You can install most flow sensors (check temp range allowed) anywhere in the seawater system and mine is installed in the water discharge thus will warn of almost any break or malfunction in the system
 
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Brooksie said:
You are right, you can fry your exhaust b/4 your coolant temp gauge even moves but I am talking about raw water flow sensors.

You can install most flow sensors (check temp range allowed) anywhere in the seawater system and mine is installed in the water discharge thus will warn of almost any break or malfunction in the system
Click to expand...

Sorry...you are correct...just before the injection would be best but not always possible.

I'm thinking of moving mine...just got to alter a few things..
 
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