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Old 08-27-2018, 12:07 PM   #1
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hose from exhaust mixer to exhaust box

Gentlemen
I have a 2016 mainship 34 Trawler twin engine. Does anyone have experience in changing out the 4.5 in. hose from the engine exhaust/water mixer box to the exhaust box in the boat. The mechanic says the hose is starting to fry and recommends replacement. My concern is can this be done with the boat in the water. ie. is the exhaust water box above the water line alowing changing the hose without flooding.

Thank you for your help
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Old 08-27-2018, 12:16 PM   #2
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Yes should be able to be done... as there should be no water in that segment (usually)......just as important, is why is it frying?

I have done it on my last boat that was a turbo and I forgot to open thd seacock.....and lofscof times on thd assistance towboat because of sucking up stuff and those are all explainable.

What's up with yours?
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Old 08-27-2018, 01:00 PM   #3
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psneed
Appreciate your response

Not sure...Mechanic who worked on my dripless looked over the motors also and says it looks

like the hose could burst as the hose is worn he highly recommend replacement

I'm courious about your problem did you also burn out your raw water impellers and anything else
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Old 08-27-2018, 01:59 PM   #4
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No to the impellers but they very well could have under different circumstances.

Unless there is a hole or some sort of distortion in the hose, pretty hard to know if you have turned your exhaust without taking the hose off...unless you smelled it.

Too many mechanics ALMOST know what they are talking about. This AM an electrical, former Navy guy was trying to tell a friend what might be wrong with his EFI Crusader gassers. He kept jumping back and forth with diesel stuff ( he does a lot of gensets, but not the engine end). Even tried to use some a examples ok f how his ships generators would hunt.

All sonded good but a 15 minute conversation wound up with more roads in the wrong direction than helping.
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Old 08-28-2018, 07:17 AM   #5
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You might be right. My friend who also has a 34 Mainship had the hose go while away... but his problem was duo to the clamps securing the hose broke.
What a mess it made in the bilge area
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Old 08-28-2018, 08:59 PM   #6
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No real help but a 2016 with hose problems ?? I'd want to see it in person.
No way a hose should only last that long...
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Old 08-28-2018, 10:11 PM   #7
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Not very old hose to have gone bad. Usually you get about 10 years. Unless your impeller is isnít pumping enough water. Have you had any overheating on your engine?
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Old 08-29-2018, 04:51 AM   #8
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my mistake...I must be getting old...2006 not 2016 so the hose is 12 years old.....understand clamps has go but has anyone ever experence a hose bursting???
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Old 08-29-2018, 06:41 AM   #9
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I have had them split and spray exhause water all over...no you dont want that as it often makes a corrosive mess.

Fortunately only had that on the assistance tow boat.

Wrapoed it with duct tape for weeks till the boat could be serviced. Even burned through the tape a couple times a week.
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Old 08-29-2018, 07:34 AM   #10
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my mistake...I must be getting old...2006 not 2016 so the hose is 12 years old.....understand clamps has go but has anyone ever experence a hose bursting???
Now that is important! I believe you are referring to the hoses that connect between the elbows and the muffler. But there are things more important that should have your attention. The thingy that connects to your exhaust manifold is called a riser and most likely it has what is called an elbow attached to it. Yes, they are heated with the exhaust gases but are cooled with raw water being injected into the pair.

The concern! This pair as I described has a limited life and if the riser should fail, it is going to cost you BIG BUCKS, MAYBE A NEW ENGINE!

If your engines are raw water cooled instead of fresh, the exhaust manifolds will also need changing periodically, recommendation is every 5 years! Unless you know the history of your engines such as when these components were last changed, you should consider replacing them before you kill your engines.
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Old 08-29-2018, 07:38 AM   #11
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The hose from the mixer to the muffler should all be above the waterline, on twins I would think even more so.

You can confirm if the hose needs replacing by disconnecting and looking inside it with a flashlight. Hose will fail from the inside out and will typically delaminate inside with visible evidence of delamination.

I prefer non wire reinforced exhaust rated hose as a replacement over wire reinforced hose. I have seen too many cases of the wire corroding and expanding and causing premature hose failure. Wire reinforced hose is typically necessary for intakes where hose collapse might occur, not necessary in properly supported exhaust hose in a diameter like 4.5"

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Old 08-29-2018, 07:52 AM   #12
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While silicon hoses have their virtues...don't be fooled into believing when they say "high temp" that it means they cant be burnt through.
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Old 08-29-2018, 09:14 AM   #13
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my mistake...I must be getting old...2006 not 2016 so the hose is 12 years old.....understand clamps has go but has anyone ever experence a hose bursting???
Bursting implies that the hose contains pressure that might be suddenly released- this isn't the case. The hose isn't pressurized more than a few inches of backpressure. When it's near end of life, the hose will start to crack and seep seawater. The heat will usually drive off the water so you'll see salt crystal trails at the leaks. As others have indicated, you probably won't see much evidence unless you look inside the hose. If the hose has been overheated/burned inside, determine WHY it is failing and make sure the underlying problem is dealt with before simply treating symptoms by replacing the hose.

Your mixer ell could be at fault, so carefully inspect it when the hose is removed. If the hose is consistently running hot enough that you can't touch it, there's a cooling problem. There can be a number of causes, the seawater pump could be worn, impeller bad, the heat exchanger could be obstructed, the mixer ell could be compromised. WHY did it happen??
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Old 08-29-2018, 09:43 AM   #14
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Ok. 12 year old hose is near the recommended end of life. I would probably inspect the inside of it and if I saw and indications of a problem go ahead and replace the hose and the clamps. I would also check the cooling as stated above and see if there are any problems.
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Old 08-29-2018, 03:09 PM   #15
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I'm confused
Is the riser /elbow you are referring to, located attached to the engine (before the exhaust hose) or after the exhaust hose near the floor of the boat.
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Old 08-29-2018, 03:26 PM   #16
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elbow and riser

foggysail

Would I not get a temperature rise in the engine if the elbow/riser system was not working properly " before it killed my Engine".

My yanmars , althought 12 years old, only have 800 hours of use...

How would I know if they need changing...elbows/ isers are expensive.
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Old 08-29-2018, 07:26 PM   #17
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foggysail

Would I not get a temperature rise in the engine if the elbow/riser system was not working properly " before it killed my Engine".

My yanmars , althought 12 years old, only have 800 hours of use...

How would I know if they need changing...elbows/ isers are expensive.

I am not familiar with Yanmars or for that matter diesels. My familiarity is somewhat limited to Crusader 454 gas engines which I thought by the way was what powered your boat. So you may not have the problem I described. Have someone with knowledge look to see if your engines have the same type of exhaust cooling as that found in a Crusader. Get good advise because many engines have been ruined because of water finding its way into combustion chambers via risers.

There are engineering methods available I suspect that could configure a safe exhaust system without the fear of a riser failure that lurks in crusader engines. In fact, a close friend ignored my advise to change his and now he is expecting a bill in the range of $8-10K for repairs. If his crankshaft got damaged, he might not get by with repairs but instead a new engine.
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Old 08-29-2018, 08:12 PM   #18
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Hey Jann,


I'm assuming you have 4LHA-STP's on your boat, 240 hp, which is what we have on our 2005 Mainship. If so, here is a source for exhaust elbows:
https://www.ebay.com/itm/Stainless-S...ZXWGpz&vxp=mtr


I changed mine out 2 years ago, they were overdue, so if yours are original they are due as well. it's not so much about hours as it is about age in elbows.



These elbows are much less expensive than the OEM parts, and also stainless instead of cast iron, so they should, in theory, live longer. The same guy who cast these also sells a mixer elbow, which I don't have a link for, but should be easy to find with a little looking.


I was very impressed with them and have had good luck so far. I think all told for both sides they will save you around $750 over OEM.


Take it for what it is worth and good luck.
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Old 09-02-2018, 05:40 AM   #19
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Appreciate your comments
I run fresh water throught my engines after every use...I'm hoping that will protect the riser and elbow.....I definately am going to change out the exhaust hose...but I really don't have the money for 2 risers and elbows...so I may let that go unless I see rust spots in the mixer when I remove the hose.

I need a mechanic as that wire hose is too ridgid to remove.
Any comments
thanks
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Old 09-02-2018, 06:20 AM   #20
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Get in there with a hacksaw and cut it into manageable pieces. You may get lucky and be able to manhandle it off the riser, but you may have to cut it off. I have used a thin flat screwdriver between the riser and hose to make just a little space, then you can cut a little at a time and you cut and tap the screwdriver. I have used a dremel tool with excellent results. Die grinder, a mini-hacksaw would be slow going but would work.



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I need a mechanic as that wire hose is too ridgid to remove.
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