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TOPIC: 4788 - 330 BT6A Cummins Exhaust system water leak

4788 - 330 BT6A Cummins Exhaust system water leak 10 Sep 2017 18:11 #1

  • Carlo
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I have a small water leak coming out of a small crack in the metal canister where it is welded on to the water cooled elbow coming out of the turbo. I removed the asbestos jacket around the elbow and found a rusty mess. I am not sure of the purpose of the metal canister other that to convert the 3 inch (ish) metal elbow to the big black rubber hose going to the muffler. I am looking at different repair solutions. One would be to unbolt the 90 deg. elbow at the Turbo and remove all the hoses connected to the canister, then take them to a welding shop to be repaired. I am deathly concerned about break the bolts that hold the elbow on to the Trubo. The second solution would be to clean up everything in place and have a welder come on site and re-weld the two parts in place.

Does anyone have an experience or advice on this problem?

Cheers

Carlo

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4788 - 330 BT6A Cummins Exhaust system water leak 10 Sep 2017 18:43 #2

  • The Other Gary
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Carlo, that is your mixing elbow and important for proper exhaust water mixing. Take both of them off and take them to a good stainless welding shop for inspection and repair.
There may be other cracks and /or pinholes as well. If you cut the insulation wrap carefully it an be reused with an additional layer of heat wrap.
The 4 bolts attaching it to the turbo are easy but hard to reach. The steel gasket should be replaced at the same time.

greenwatermarine.com/products/cummins.html

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"Adios Dinero"
1997 3988 with new 330 Cummins
Photo Credit: Whiskywizard

4788 - 330 BT6A Cummins Exhaust system water leak 11 Sep 2017 00:33 #3

  • higgins_jr
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Gary, I'm unsure of what mixer design is on your craft, but on many 47's, it's a can mixer arrangement that takes raw water away from the turbo neck flange, per the pic attached. The pics from the website you posted had the heat exchanger raw water feed real close to the turbo neck flange.

I had rusted/stuck bolts and the service clown decide to hacksaw thru the elbow, and reweld it later, which he did do after the repair to fix the drip, which was on the bottom of the can, not the elbow. Depending on how bad the rust is, it could be repaired but the rest of the can needs to be assessed as well. I had to take the turbo off too to get the stuck bolts out. The cans are still available from National Marine Exhaust out of Seattle as well as the wrap around blankets to fit.

Cheers

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John H
Brisbane QLD Aust
"Harbor-nating"

2000 - 4788/Cummins 370's
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4788 - 330 BT6A Cummins Exhaust system water leak 11 Sep 2017 02:17 #4

  • ksanders
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The thing you arre refering to is made by National Marine Exhaust http://nationalmarineexhaust.com

It's an exhaust elbow. It costs about $650, and generally is able to ship in a couple day lead time.

Don't screw around with a welder. Just order a replacement. You can DIY the job if you are really handy, and are comfortable with hand tools. I hired a guy to help, as it's easier with two people.

This is a manitenance item. I had one go out at 5 years, but I thoink they have a longer average lifespan than that.

If you call therm they know ecactly what you need and can take your order over the phone.

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KEVIN SANDERS
4788 LISAS WAY
SEWARD, ALASKA
www.mvlisasway.com
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4788 - 330 BT6A Cummins Exhaust system water leak 11 Sep 2017 04:50 #5

  • Woodsea
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Carlo,
I totally agree with Kevin. The exhaust cans have a finite life. If they fail, sea water goes back thru the turbo into the #6 cylinder. I replaced ours when we first got the boat. They were at 14 years 1700 hours and were starting to show signs of failure. Scott at national marine exhaust recommends replacing at 10 years for a salt water application. Maybe a guy could get more if the exhaust was flushed with fresh water when laid up.
Steve
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2000 4788 w Cummins 370's, underhulls, swim step hull extension
12' Rendova center console with 40HP Yamaha
MV Kia Orana
Currently Alameda CA

4788 - 330 BT6A Cummins Exhaust system water leak 11 Sep 2017 20:49 #6

  • Carlo
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Thanks Guys for your input. I have had conversations with John Higgins, Tony Athens and Scott at National. I am ordering a new elbow/can assembly from Scott. They now cost $1499.00 USD plus shipping. All three gentlemen were very helpful in explaining what happens when these units start to deteriorate.

Tony wrote a good article about this topic. It is worth reading. www.sbmar.com/articles/marine-exhaust-systems/

Carlo

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4788 - 330 BT6A Cummins Exhaust system water leak 11 Sep 2017 22:51 #7

  • TenMile
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Carlo -- I did mine on my 4BTA's last fall.

As others have pointed out, you may find that the bolts that hold the flange to the turbo are impossible to remove. The PO of my boat had someone actually weld one of the flanges to the turbo itself as the bolts had rusted off. I found it easier to remove the entire turbo and exhaust can and take it to a machine shop. They got the old bolts out and cleaned up the mating surfaces. If you do remove the turbo, you need to replace the gaskets as well -- you can get these from any Cummins parts dealer.

Also budget to replace the section of exhaust hose as well rather than reuse the old stuff. It too has a finite lifespan and will run you about $50 per engine.

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Terry
1999 Bayliner 3388
Twin Cummins 4BTA
Fisherman, Cruiser, Boaticus-enthusiasticus-maximus
Member Royal Victoria Yacht Club
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