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Old 09-02-2018, 04:22 PM   #1
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Exhaust Hose: Wire or no wire?

I am getting ready to replace the exhaust hose on my Yanmar 4LHA-stps. The current set up is a continuous run of 4" with wire from the elbow to the muffler.


For various reasons, I'm going to change it up a little, going with about a 7' run of hose to a 4' long piece of fiberglass exhaust tubing to a 1' section that goes through the aft bulkhead of the engine room and connects to the muffler, which is in the lazarette.


There will be a gentle curve in the 7' section as it drops from the elbow down about 2 feet to the tubing. The fwd end of the tubing, very close to the connection to the hose is supported by a cradle. There are no hard bends.



If possible, I'd like to avoid using the wire reinforced hose, mainly just because it is easier to work with. I'm sure I'm going to use no wire for the small section that goes through the aft bulkhead as that connection is going to be a tough one to do.


What do you guys think about no wire for the long section?
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Old 09-02-2018, 04:32 PM   #2
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Its fine unless you need really rigid hose for support, which one rarely does.

When I said fine I meant just to go wireless hose, too drastic of an exhaust system change involves more than a couple considerations
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Old 09-02-2018, 05:05 PM   #3
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I am curious why you are lengthening the whole assembly and introducing a curve. My concern would be increasing exhaust back pressure. I'd really encourage you consulting a good mechanic familiar with your engine and marine exhaust issues.

As for what hose, I'd recommend the blue silicon stuff; pricey but great for the purpose at hand and a lower total cost of ownership in the long haul. But please, get an expert opinion.

You are in Carabelle so not all that far from Marine Exhaust Systems of Alabama for one, over in Fairhope. And Dog River Marina there is a good yard.
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Old 09-02-2018, 05:14 PM   #4
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Well, this is an opinion not from a mechanic, but from a retired chemical engineer who knows a thing or two about pressure drop in piping systems.

I bet you are not going to increase the overall length significantly, maybe a foot or two. You are going to introduce a couple of new of connections to the fiberglass tubing and the ID of that tubing will be smaller than the 4" hose but it will be smooth unlike the hose, so maybe no effect. But all in all I don't think you are going to increase the pressure drop significantly and I think that 4" is plenty big enough for that engine.

You could measure the pressure drop before and after and compare to Yanmar installation requirements. I wouldn't bother.

So do it and use blue silicone hose as others have recommended.


But why are you replacing the existing hose that is only 13 years old. Did it overheat and cook?


David
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Old 09-02-2018, 06:39 PM   #5
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I just replaced the 2" wire reinforced generator exhaust hose. The existing was leaking,old age I`d say, possibly original. There was no specific issue with the wire reinforcing,seemed tough and unrusted both ends when I made cuts with the Dremel. The hose rises from the muffler ,has 2 bends both around 120 degrees, before dropping to the skin fitting.
I replaced with more of the same,it was more flexible, not externally corrugated, but still wire reinforced. It proved much easier than expected, maybe there have been advances in reinforcing flexibility.

My research suggested silicone needs rigid bend sections. That would require multiple clamps, I didn`t think it was a good idea.
But, the guy who replaced my 4" main engine hose on a Perkins 6354 looked to have gone several rounds of boxing with a bear, so your job could be a lot harder!
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Old 09-03-2018, 06:21 AM   #6
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If hose will have any curve in it, it needs to be wire wound. "Softwall" or no-wire hose will kink with any bend. I use softwall for short connecting sleeves between hard tube and mixers, etc. Softwall also will vibrate more and create more noise in ER.

My favorite way is to run most with FG tube and use hose sleeves only to connect things.
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Old 09-03-2018, 06:25 AM   #7
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To my mind the silicone may help IF the sea water to cool the exhaust is lost , as the silicone can handle more temperature before melting/ burning.
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Old 09-03-2018, 06:27 AM   #8
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Quote:
Originally Posted by djmarchand View Post
Well, this is an opinion not from a mechanic, but from a retired chemical engineer who knows a thing or two about pressure drop in piping systems.

I bet you are not going to increase the overall length significantly, maybe a foot or two. You are going to introduce a couple of new of connections to the fiberglass tubing and the ID of that tubing will be smaller than the 4" hose but it will be smooth unlike the hose, so maybe no effect. But all in all I don't think you are going to increase the pressure drop significantly and I think that 4" is plenty big enough for that engine.

You could measure the pressure drop before and after and compare to Yanmar installation requirements. I wouldn't bother.

So do it and use blue silicone hose as others have recommended.


But why are you replacing the existing hose that is only 13 years old. Did it overheat and cook?


David
I may have misread the OP it sounded at first as if he was going to add length.
Ski's point about bends is well taken.
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Old 09-03-2018, 08:41 AM   #9
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Thanks for the responses guys.


I'm not adding any length to the exhaust run, nor am I changing the "shape" of the run. The only way that it will be different is that I am adding a section of hard tube into the run. The section of hose that I'm replacing with tube is already straight. I can't see how it would change the back pressure at all as I am not adding any length or bends.



The tubing is right over my house bank. The wire in the old hose corroded badly in that section, which is why I am having to replace it. I'm pretty sure that the corrosion was the result of a catastrophic battery/charger failure, and though I don't expect that to happen again, the hose is still really close to the battery bank, so I'm being safe here.


I'm getting the tubing from a place in Stuart (that's where my boat lives) who specializes in exhaust systems and builds custom risers. He thinks adding the tube is a good idea, but I haven't asked him about wire or no wire.



BTW, the blue silicon hose is too expensive for me in the long section, if it's a choice between that and the wire hose, I'll just have to fight with the wire.



The connection to the muffler is goint to be the hard part as the muffler is in the lazarette behind the generator. It's nearly impossible to reach from inside the lazarette without moving the generator. But the muffler connection is only a few inches aft of the bulkhead separating the lazarette from the engine room and I have good access to it on the ER side. So I am going to try cutting an access plate through the bulkhead from the ER side which will allow me to reach the muffler connection.


It's still not going to be easy to get the old hose off there and the new hose on, so I'm going to go with the softest, slipperiest hose that will work for that section which runs from the aft end of the FG tube to the muffler. It's only going to be 12 to 18 inches long, so I'm sure silcon unreinforced hose will work there.
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Old 09-03-2018, 10:37 AM   #10
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As a rule soft wall hose (no wire) will outlast hardwall. Like Ski said, soft wall will kink pretty easy.
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Old 09-03-2018, 02:35 PM   #11
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I like to see the least possible amount of hose, and lots of fg tubing, preferably with just short pieces of hose to tie the fiberglass together.
Hose is vulnerable in many ways, As the OP is already been made aware.
Long hose runs are seldom properly supported, resulting in residual water in the system that can cause all kinds of havoc, including catastrophic failure of the motor.
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Old 09-03-2018, 04:07 PM   #12
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FG tube real close to the injection elbow will deteriorate as fast or faster than hose when exposed to high heat....it can charcoal and disintegrate

Thats why it is important to use the internal metal clamp inserts or the FG can break up and fall out of the hose.

I don't see where hose is intrinsically inferior, but every exhaust system is a little different and could have different requirements. And as usual, subject to install issues.
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Old 09-04-2018, 09:44 PM   #13
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Well, step one is done.



My buddy came over and helped me get the old hose off. By lying on his side he was able to worm his way in behind the generator far enough to reach the hose clamps. I squeezed into the engine room, cut off the hose about 18 inches before the bulkhead, then drilled a hole straight through it. I then inserted a two foot long piece of stainless rod through the holes in the hose and tourqued like crazy while he pushed on the back end with a flat head. Took us two hours but we got it loose.


My hands are bleeding from the rusted wire that came through my work gloves, and I'm beat.


But we didn't have to move the generator or cut a hole in the bulkhead.


Install will be waaaaaay easier.
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