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Old 12-04-2017, 11:03 PM   #1
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Beneteau ST 44 potential sea water intrusion

Tom (sunchaser), I and others are helping Richard (don't know if he is a TF member) over on Boatdiesel figure out why both turbos on his twin Volvo D4 powered Beneteau ST 44 recently failed. The pics he just posted on boatdiesel definitely show corrosion in the turbos due to sea water intrusion, probably from the exhaust system.

I would encourage all TF members with this boat and engines to review this problem on boatdiesel at http://boatdiesel.com/Forums/index.c...hread_ID=63733 to see if their boat may have the same problem.

I suspect that it ruined Richard's first pair of engines (Volvo replaced them) and it has now ruined the turbos on his new engines and will eventually probably ruin the new engines if not corrected.

He posted pictures of the exhaust system on boatdiesel. It has a flat run from the mixer back to the lift muffler which may let water slosh back up from the muffler.

We don't as yet know about the geometry dimensions but Richard will post them to boatdiesel once he gets his new turbos installed. Look at the attached pic to see the best geometry for this type of installation. Not all boats can achieve this and there are some things you can do if you don't have the room to do it this way.

We can continue the conversation with TF members who have concerns about this problem on this thread. We might want to start a parallel thread on boatdiesel, but for now let's stick to this one.

David
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Old 12-05-2017, 07:47 AM   #2
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I keep hearing about this sort of thing, and it astonishes me that boat builders continue to design exhaust systems this way, and that engine manufacturers accept the installations. I guess it's a calculated risk, betting that most boats are moored in calm conditions where they won't get bitten by this, and/or it will last long enough to be out of warranty....

I think I saw just this in a picture on TF recently (can't remember if it was a Swift Trawler or other boat). The exhaust from the engine sloped down to the mufflers, where a better design would have been for it to run up as high as possible in the ER, then loop down.
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Old 12-05-2017, 08:55 AM   #3
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Is this a danger scenario particular to Beneteaus? If not, there are a lot of unsafe boats out there, if Iím reading the diagram correctly.

On our Defever, the exhaust mixer spillover is at or just below the waterline and the ďhumpĒ in the exhaust hose is at least a foot higher than the mixer. Yet I havenít heard about an epidemic of engine back-flooding. What am I missing?
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Old 12-05-2017, 09:37 AM   #4
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Quote:
Originally Posted by djmarchand View Post
Tom (sunchaser), I and others are helping Richard (don't know if he is a TF member) over on Boatdiesel figure out why both turbos on his twin Volvo D4 powered Beneteau ST 44 recently failed.
Believe that would be Rclarke246.
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Old 12-05-2017, 11:11 AM   #5
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Is this a danger scenario particular to Beneteaus? If not, there are a lot of unsafe boats out there, if I’m reading the diagram correctly.

On our Defever, the exhaust mixer spillover is at or just below the waterline and the “hump” in the exhaust hose is at least a foot higher than the mixer. Yet I haven’t heard about an epidemic of engine back-flooding. What am I missing?
What you describe in your Defever is very typical of sailboat exhaust systems. They are not inherently safe according to the diagram. The engine sits low and the lift muffler is also low. But there is a very high exhaust loop after the lift muffler. That loop is high enough to prevent waves from pushing sea water up and over the loop.

But if the loop is not high enough and I suspect that is the case on Richard's ST44, sea water will go over the loop, ultimately fill the lift muffler and back flood the turbo.

There are ways to mitigate this, but lets let others chime in first before discussing them.

And if you follow boatdiesel for long, you will hear of many situations of sea water intrusion corroding turbos. I'll bet that at any one time there are 1 or 2 active threads on this topic at boatdiesel and at least a dozen new ones each year. So boat and engine manufacturers aren't doing much to avoid bad exhaust installations.

There are also many, many boat owners who replace their turbo thinking it is a consumable item. In almost all of these cases it is due to sea water intrusion and they have no clue what is happening. Turbos rarely die a natural death.

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Old 12-05-2017, 11:18 AM   #6
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I put some thoughts on the BD thread.
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Old 12-05-2017, 12:52 PM   #7
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out of curiosity, what does it cost for a new turbo?
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Old 12-05-2017, 01:44 PM   #8
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I'd suggest any owners also contact Beneteau and get what they have to say on this issue. I'd want some official statement from them regarding my own boat.
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Old 12-05-2017, 02:08 PM   #9
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Yes, someone please share contact name/email/phone. would be best they address this before failure. I specifically avoided buying a particular boat a few years ago because it had a major exhaust/cooling design flaw that everyone was struggling with. IIRC both the engine manufacturer and boat builder partnered together to try to fix.
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Old 12-05-2017, 02:33 PM   #10
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I would prefer that this thread focus on fixes rather than point fingers at Beneteau or Volvo.

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Old 12-05-2017, 02:51 PM   #11
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I would prefer that this thread focus on fixes rather than point fingers at Beneteau or Volvo.

David
as a part of that would be good to understand each of their stances and what their recommendations (if any) are to prevent from happening on all the ST44 they have produced to-date. they likely (hopefully) have someone with advanced skills on their teams that can help address.

also, i dont think that rclarke's prior engine replacement had to do with sea water intrusion. the engines were eating oil. further, it should be noted that he probably has one of the first ST44 (if my memory serves me, he has a 2012 and that was the first year of the ST44) and therefore may be experiencing failures and such ahead of everyone else.

would be interested to know if anyone else has opened their turbos and also if Beneteau has introduced any design changes in the exhaust configuration since 2012.
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Old 12-05-2017, 03:55 PM   #12
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Hope this isnít too much drift, but on the subject of flooded engines, I found a side view of an older Defever 44 . . . maybe an Ď82, when they still had masts and FL 120s powering them. But the basics are pretty similar to later models. The engine exhaust is about 6Ē above the design WL and, moving forward, the exhaust hose slopes upward about 2 feet before plunging down to the muffler. The exhaust mixer is, as I suspected, at the water line.

Granted, few if any Defevers of this vintage had turbos. But if this is an inherently unsafe design, Iíd be interested in knowing why flooded engines arenít a topic Iíve ever seen discussed on the Defever forum.
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Old 12-05-2017, 04:34 PM   #13
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The engine exhaust is about 6” above the design WL and, moving forward, the exhaust hose slopes upward about 2 feet before plunging down to the muffler. The exhaust mixer is, as I suspected, at the water line. .
That design as you describe sounds similar to my vessel. I'd guess that DeFevers made in the past 25 years are all with turbos. The drawing does seem clear enough to see similarities between old and new.. Three things on my vessel:
  1. The downward slope from the ER area to the sea is "extreme" thus preventing waves or water coming into vessel when engines off. This good angle is allowed by the high salon floor above the engines. As well, retained water in hose flows to stern except for smaller amount that may flow back downhill to muffler.
  2. On mine the water lift muffler is sized to accept about 3X the volume of drain water in the hoses when engines are shutdown. My water lift is well less than half full at shutdown, I know because I've pulled hose off to peer into muffler.
  3. I have working vent loops on the raw water line going to the elbow thus stopping any tendency for siphoning/backfilling through engine or stern tube following shutdown.
I'd guess there are good reasons you don't read about engine back flooding on the DF forum. they are rare or non existent. DeFever picked up his wet exhaust designs from the crew and officer boats he designed for use in the Pacific during WWII. Big waves and issues when you're dropping a Captain's wet exhaust gig from the deck of a battleship into the rolly seas below.

Then he began designing offshore tuna charter boats for SoCal and Mexican waters, never calm there and engines are frequently off. Surprisingly the incidence of the engine back flooding for the thousands of Taiwanese and Chinese built trawlers don't seem too common if at all. DeFever design pirates at work?

Certainly Ed Monk knew how to do it as well. His exhaust designs litter the landscape in past, present and future wet exhaust vessels across many brands.
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Old 12-05-2017, 05:03 PM   #14
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Let me restate this again. The diagram I attached is the ideal. All water even if it completely floods the lift muffler will run back out over the exhaust loop to the transom before it backs up into the turbo because the spill over point just before the mixer is higher than the exhaust loop.

The Defever with its 2' high loop is enough to pretty well insure that no wave will back up into the lift muffler. But if it possibly did it could back up to the turbo if the muffler filled over time.

So the Defever design is good, and it works, but due to its geometry it isn't inherently safe like the picture.

BTW, that picture comes from Tony Athens, the Cummins/Yanmar guru formerly of boatdiesel who has his own website now at sbmar.com/community.

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Old 12-05-2017, 05:26 PM   #15
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Is there any relationship between the sea water affected turbos and the observed water leak where the exhaust line meets the transom?
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Old 12-05-2017, 08:19 PM   #16
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Sent an email to my list of Beneteau contacts to see if they have an "official" position on the exhaust/turbo issue.

Stay tuned.......
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Old 12-05-2017, 09:30 PM   #17
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Thanks for the background, Tom and Dave. Just one more reason Iím glad I donít have turbos.
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Old 12-05-2017, 09:47 PM   #18
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I would prefer that this thread focus on fixes rather than point fingers at Beneteau or Volvo.

David
I would prefer the problem didn't exist. However, I think in working on a fix, Beneteau should be involved. They should have the most knowledge of the issue. I don't see speaking to Beneteau as pointing fingers at all. You're asking for their observations, advice, assistance. Everything I've seen so far about Beneteau and Volvo's responsiveness to problems has been positive. They've shown willingness in many cases to go above and beyond. They need to be involved.
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Old 12-06-2017, 12:03 PM   #19
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Can't comment specifically on the Beneteau exhaust issue (although I did own two of their sailboats in a past life). Thought I'd throw out some observations over the years of doing my own boat maintenance and helping dock neighbors with their power systems....

I've worked on a couple engines that had rust/carbon buildup in the turbo body that had blocked the exhaust blades from turning....resulting in black smoke under load and reduced top end power. Fortunately, they were resurrected by removing the exhaust elbow, scraping/vacuuming the loose buildup from the turbo body, spraying a LITTLE bit of PB Blaster in the blade area, and rotating the turbo shaft with a socket and ratchet until no contact with the turbo body. I attributed the rust to what I call "backspatter and misting" (Texas term) from the water lift muffler, as these owners were known to idle their engines too much in my humble opinion. My thought is that low speed operation doesn't do a good job of blowing the water out of the muffler, and you get a warm salty mist/splatter back up the exhaust tube to the turbo. This is why, after cooldown, I always rev up my engines to clear the excess water from the mufflers before shutting down my engines.

Just my observations...YMMV, and you can stick it in your hat to chew on later, or chunk it on the fire with the rest of the cow chips!
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Old 12-06-2017, 12:45 PM   #20
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My thought is that low speed operation doesn't do a good job of blowing the water out of the muffler, and you get a warm salty mist/splatter back up the exhaust tube to the turbo.
Good point. One can always pull a hose of the muffler and see how full of water it is after a "normal" shutdown. Whether Beneteau or other vessels.
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