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Old 11-04-2015, 12:55 PM   #1
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Exhaust hose

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I recently replaced the piece of exhaust hose that runs from the elbow to the muffler. It had collapsed inside-- see pic.

I didn't look at the run of hose from the muffler to the exhaust outlet however because I was too tired at the time. Is there a possibility that section of hose also needs to be replaced? I had hoped that since it was further from the elbow it might still be OK since it's cooler?

Why do these exhaust hoses collapse like this?
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Old 11-04-2015, 01:28 PM   #2
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Running above idle with no water flow (such as a forgotten closed seacock)....

I have seen many a hose burn or just delaminate or a combo of the two.
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Old 11-04-2015, 03:02 PM   #3
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Low raw water flow due to a clogged strainer, a broken impeller, a plugged exhaust elbow, etc. will cause this. Or as psneeld says leaving the seacock closed even for a few minutes will do it if you have some load on the engine.

Your water lift muffler should help particularly if due to low flow. So maybe the hose downstream is ok. But I would check.

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Old 11-04-2015, 03:55 PM   #4
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Guess my view on it is that hoses are (relatively) cheap, and engines are not. When in doubt, replace.
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Old 11-04-2015, 09:19 PM   #5
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Why do these exhaust hoses collapse like this?
You must have been running very hot to do that! Only a water supply failure would cause that kind of damage.
Most certainly check the rest of the run, and the muffler for further damages, and of course, you must determine what caused the overheat condition and fix that as well.
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Old 11-05-2015, 01:08 AM   #6
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I've never run it over about 200 and that was just for a minute. It usually stays around 175-180 at the speed I run.
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Old 11-05-2015, 06:34 AM   #7
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I've never run it over about 200 and that was just for a minute. It usually stays around 175-180 at the speed I run.
That's the engine temperature in the coolant. What you have to understand is that in normal raw water flow, the raw water after the heat exchanger may be only 120 degrees before it goes into the exhaust elbow. If the raw water flow is diminished by one more more broken impeller blades or a partially block heat exchanger, the thermostat may have to run completely open to get rid of enough heat in the reduced raw water flow. As a result of the reduced raw water flow, the raw water temperature may be 170 degrees or higher before it goes into the exhaust elbow. At the exhaust elbow you may be creating steam which may be too hot for the exhaust hose. Engine coolant temperature isn't a great indicator for exhaust gas / water temperature.

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Old 11-05-2015, 08:40 AM   #8
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I've never run it over about 200 and that was just for a minute. It usually stays around 175-180 at the speed I run.
Are you the first and only owner of the boat?

This kind of failure can be cumulative. It isn't always due to a one time event.
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Old 11-05-2015, 09:31 AM   #9
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I discovered delamination in my exhaust when I added inline mufflers. They were in the form of large bubbles that probably occluded the hose by 20%. My boat is 20 years older than yours 2008. I wouldn't mess with it, replace all of it. Your picture looks really bad. If your boat is like mine the bummer is access to the straps that hold the hose in place. I had to open/cut some cabinetry to get at it.
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Old 11-05-2015, 09:34 AM   #10
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Hose can delaminate for a few reasons, heat is most likely. A common problem is at low power the water injected in the mixer does not mix uniformly and hose gets hot spots. This has no obvious symptoms, but can be checked by hand or IR gun at various low power speeds. More common than most think!!

It could be due to an engine overheat event if sea water flow was lost, but usually this is obvious because inside of hose is scorched or blistered. If due to hot spots, the heat damage is in spots, but not all over.

Or the hose could have just failed. It is multiple layers and bonding between them can be iffy.

It would be nice to check the hose downstream of the muffler if it is accessible.
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Old 11-05-2015, 10:07 AM   #11
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I don't remember the year, but one manufacturer of corrugated exhaust hose had some problems with the steel reinforcing wire deteriorating. It caused some de-lamination and even some seepage from the hose. It would be good to check all yours exhaust hoses. Did you find any white residue from salt on the outside of the hose?
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Old 11-05-2015, 11:16 AM   #12
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Quote:
Originally Posted by jwnall View Post
Guess my view on it is that hoses are (relatively) cheap, and engines are not. When in doubt, replace.
I am in full agreement. If one is bad, the rest are suspect. And too, fixing it before breakage is always cheaper. Go shopping for hose. Make sure you specify two wire exhaust hose.

There is a lesser quality exhaust hose with just one wire running through it. You want two. Reason: if you have to bend the hose, one wire will crease. Don't ask me how I know that!?! (Thankfully, that was not my boat but still, something to be aware of.)

With that amount of delamination, I'd replace every hose in the cooling system. IF your others are still good, you've got spares. I believe however you'll find problems throughout the system. Seldom would you have a problem in just one hose. That doesn't happen very often in my experience.

Good luck.

And while I'm spending your perfectly good money: if there's not access, cut it/create it. You will never be sorry to have easy access to components. Hinges and latches will let you close things up until needed.
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Old 11-05-2015, 11:57 AM   #13
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Exhaust hose

Ok. Thanks everyone.

I'll pull the hose after the muffler when I get back home and check things out.

Another thing I just thought of-- there are two exhaust outlets coming out of the built in swim platform (with poor access). The starboard side has lots of water flow but the port side does not have much flow. I guess there is a Y connection somewhere where it splits? Is that necessary to have two outlets? The genny has it's separate exhaust outlet.
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Old 11-05-2015, 12:02 PM   #14
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Exhaust hose

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I don't remember the year, but one manufacturer of corrugated exhaust hose had some problems with the steel reinforcing wire deteriorating. It caused some de-lamination and even some seepage from the hose. It would be good to check all yours exhaust hoses. Did you find any white residue from salt on the outside of the hose?

I don't remember any residue. The hose that went bad was Trident brand.

If I have to replace the after muffler hose I would have to get some of that high dollar flexible stuff. That stiff hose was terrible to work with.
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Old 11-05-2015, 12:02 PM   #15
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Ok. Thanks everyone.

I'll pull the hose after the muffler when I get back home and check things out.

Another thing I just though of-- there are two exhaust outlets coming out of the built in swim platform (with poor access). The starboard side has lots of water flow but the port side does not have much flow. I guess there is a Y connection somewhere where it splits? Is that necessary to have two outlets? The genny has it's separate exhaust outlet.
One could be a false exhaust outlet and the water you are seeing is from one of your A/C units.
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Old 11-05-2015, 12:05 PM   #16
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Exhaust hose

Quote:
Originally Posted by Ski in NC View Post
Hose can delaminate for a few reasons, heat is most likely. A common problem is at low power the water injected in the mixer does not mix uniformly and hose gets hot spots. This has no obvious symptoms, but can be checked by hand or IR gun at various low power speeds. More common than most think!!

It could be due to an engine overheat event if sea water flow was lost, but usually this is obvious because inside of hose is scorched or blistered. If due to hot spots, the heat damage is in spots, but not all over.

Or the hose could have just failed. It is multiple layers and bonding between them can be iffy.

It would be nice to check the hose downstream of the muffler if it is accessible.

I have an IR gun. Will check for hot spots. Thanks.

The downstream hose access is pretty crappy but I can pull it off the muffler pretty easily, standing on my head. 😢
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Old 11-05-2015, 03:23 PM   #17
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Usually it is the hose right aft of the mixing elbow for a few feet or less.

With the hundreds of grounders I get unstuck each year, it is rare I get more than two or three seasons out of the rubber/silicone hose just aft of the mixer.

Granted it is a gasser 454, but I often pull and pull hard for a few minutes where water flow has all but stopped, till I am well into a coolant overheat alarm.

Really no big deal. I have conducted weeks worth of tows with just layers of duct tape around the burned through spots on the hose. When exhaust is smelked, add a few more layers of duct tape to cover the new burn through spots....
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Old 11-06-2015, 09:10 PM   #18
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Psneeld,
Don't think I'd be bragging about that kind of maintainence!
Why not make replacing that piece of hose an annual PM item?
Wouldn't you feel silly if you had to be towed home by a customer?
To the OP,
You have problems with your exhaust system because it is not properly installed. The pic you show, if shot from above, shows that the mixing elbow is oriented straight up, the worst possible scenario for a wet exhaust exit.
Mean old Mr. Gravity is dumping raw water back into the turbo and beyond every time you shut the engine off.
I suspect the "shower head" at the elbow is plugged up, thus the burnt hose without overheating.
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Old 11-06-2015, 10:03 PM   #19
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I worry more about my exhaust hose than anything else on my boat. It's a small layer that keeps my boat from sinking. I think it's also fragile because of the hot exhaust gas.
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Old 11-06-2015, 11:19 PM   #20
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Quote:
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You have problems with your exhaust system because it is not properly installed. The pic you show, if shot from above, shows that the mixing elbow is oriented straight up, the worst possible scenario for a wet exhaust exit.
Mean old Mr. Gravity is dumping raw water back into the turbo and beyond every time you shut the engine off.
I suspect the "shower head" at the elbow is plugged up, thus the burnt hose without overheating.
It appears to me from what little of it I think I see in the picture that the outlet for the elbow is horizontal. And I'm guessing has a hump in it between the inlet and outlet ends.
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