Exhaust Elbow Blues, Reprise

Raise your hand if you thought we would have some trouble with that exhaust set up on Galapagos during our recent shake down trip from Astoria, Oregon to Tacoma.  Yeah, don’t gloat. Because our hands are raised, too.  If you’ve been following the Drama of the Exhaust System, you’ll recall that we had a fancy new engine exhaust pipe made to fit the boat because we were worried that water would back up into the engine, drowning Hiram and making us dead sad. If you are new to this series, read about that here and here to catch up with the rest of us.

The new pipe fit like it was made for Galapagos because, duh, it WAS made for Galapagos to the tune of (Put coffee mug down here) an amount of money that is very large.  When you pay several hundred dollars for a specially machined piece, you kind of think things would be right but that’s where you would be wrong.

Freshly installed and wrapped. This tape turned out to be really good.

From the get go, Mike was concerned about the weld holding the new piece of metal pipe to the flange that was used to attach the thing to the Beta. It just didn’t seem that the piece had enough support to keep that particular joint intact but the mechanic who fashioned the piece assured us that it would be fine. We wanted to believe him because we really were anxious to turn the page on that chapter of the refit. The pipe was pretty. It fit nicely. The kid who made it was a nice kid. Hiram hummed along perfectly well. Mike added rubber washers to the support on the right, wrapped the thing in insulating tape, and vowed to keep his critical eye on it. We figured it would eventually be a problem but we wanted to get going bringing Galapagos up to Tacoma. What could possibly go wrong?

All was well until we were anchored in Bellingham Bay ready to visit our son Andrew for a couple of days. Mike had been doing his usual checks in the engine room and I could tell by the cut of his jib something was amiss. Then the cursing began. It’s always quiet, but it sounds even worse that way and after the time he found water in our new engine’s oil, whenever I hear silent cursing coming from the engine room, I have a post traumatic experience. He found that the weld had separated just where he’d been concerned it would, and what was holding the pipe together was the insulating tape. And because of  the leak, the exhaust gases were now allowing water to make its way back toward the engine! Oy. When we examined the broken weld, we saw that the piece had been butt-welded, not beveled or supported in any way. Sheesh. Do we need to learn to weld in order to see that things are done right?

You can see the complete break in the middle of the photo. Ouch.

You can see the complete break in the middle of the photo. Ouch.

He removed the tape, which was black on the inside from engine exhaust. The pipe was in two separate pieces. Mike attempted a temporary fix using high temperature silicon tape but the gas pressure made that fix very temporary. There was nothing for it but to get the thing repaired. I held my breath as he checked the engine oil. No water. Praise the powers that be. Hiram was safe. Another bullet dodged; another withdrawal from the Kitty of Karma. We better start making some deposits there.

These are the times that try the souls of boat owners and we feel extremely lucky that this happened in Bellingham when we were safely anchored and had access to a car and services.  Really, life was incredibly good just then and no stinking exhaust pipe was going to ruin our time. Mike thought we might be stuck in Bellingham with the exhaust system blues for a few days. I can think of worse places to be. Andrew rescued us with his car and he and Mike carefully rowed the piece to shore. 

Mike took the piece to a place he had called (thank you, Iphone), and they referred him to someone else, etc. By the following day he had located Chad Peterson of Peterson’s Welding and Fabrication.  After consulting with Chad (our new best friend)  we left the parts with him and spent our waiting time purchasing aluminum stock and doing some other fun things we’ll write about later. It was a good day, one that made us look forward to being retired and having time to just go with the flow.

Mike planned to use the aluminum stock to make new support struts and called our loyal mechanic, Shawn, who had also been a little concerned with the exhaust pipe installation. Thankfully he is very responsive at picking up the phone when Mike calls. You’d think he’d be tired of hearing from us by now. He had some good ideas to add to Mike’s good ideas and a plan was formed.

Shawn maintained that the pipe needed to vibrate in time with the engine vibration and therefore needed to be supported by struts that were attached to the engine. That made sense to us. Hell, what do we know?  So in addition to beveling and welding the pipe, Michael asked Chad to add a cross brace with holes in it to create a more stable geometric form that would also provide landing points for the new support struts. That way the pipe and the engine could both sing the same song.

In deep mano a mano consultation with Chad. The amount of testosterone in this workshop was mind boggling. I had to get some fresh air.

A few hours later we picked up the newly welded piece. This time the two parts were beveled to allow a greater amount of surface area to be welded. We can only hope. It all looked great (just like it did last time… just saying) so we paid Chad less than I thought it would be and returned to the boat. These kinds of things are why I still work.

Mike tests the tensile strength of the finished piece. He is pleased.

Installed and ready for new supports. There is so much more structural integrity just with the crosspiece added. Geometry, people. Geometry. Live and learn.

Back at the man cave aboard Galapagos Mike created two support struts for this piece of metal art we call an exhaust ‘elbow’ and found places to attach them to the engine. We had picked up some aluminum flat and angled stock while waiting for Chad to work his magic. Without shore power, Mike was limited in how much actual cutting and drilling he could do to build the struts and aluminum is much easier to work with than steel. He also decided that he would leave the insulating tape for later so he could keep a close eye on the thing. A very close eye.

We left that afternoon and spent a lovely evening at little Eliza Island, just an hour from Bellingham. Everything was holding thus far. We know this because every time I looked up Mike had his head in that engine room, gimlet eye focused narrowly on Hiram’s elbow.

Two supports. He may put in a third one but this is it for now.

Two supports. Notice one is a flat piece and one is an angled piece. There will be a test on this information later.

The following day we had a long motorboat ride with some minor sailing down Rosario Strait. The pipe had plenty of opportunity to break if it was going to do so right away. All went well and we pulled into Griffon Bay to spend the evening, planning to cross the strait the following day.

I’d like to say that this was the end of the story, but alas, our karma doesn’t work like that in this instance. This sentence is what is known, in literary terms as ‘foreshadowing’, a term which, as used here, means ‘giving a broad hint about things to come’.

We had a lovely sail across the strait the next morning, ending up amazed at how much distance this boat can travel in a day compared to Moonrise and how it can do 12 knots around Wilson Point and never even think about surfing. Speed demons!  We motored some, but sailed more and still had record speed in the crossing, for us. We made it to the south end of Whidbey Island before anchoring for the night in the currents of Useless Bay.

Anchored in Useless Bay.

We had more sailing on the final leg of the trip. In all, we sailed a good part of this trip from Astoria to home. Even so, one of the supports turned out to be a sacrificial piece. The day after we pulled into our slip at Foss Harbor, Mike was doing his thing checking all things Hiram in the engine room. I heard that small little cursing I’m beginning to know so well. 

Oh yeah. The flat piece of stock sacrificed itself on the alter of vibration for the sins of the exhaust elbow. It took the load and the load broke its back. Pause for that moment of silence.

We have some more ideas about how to solve this problem but we want another pair of eyes to take a look so Mike will be busy finding someone in the Tacoma area who can give us another opinion. Looking at the system as it’s set up, it seems to us that on the right (in the photos) the rubber piece that connects the pipe to the water muffler serves to absorb the shock of the vibration. There is no such piece on the left, and this is too bad. Even if the thing vibrates in time with the engine, there is too much vibration for it to hold for long.

My idea was to have the thing cut into two pieces again, take part of the rigid pipe out, and insert a rubber piece on the left side. That would surely absorb the vibration on that side. Mike says that’s not an appropriate place for a piece of rubber. I believe him because, again, what do I know? But surely there is an equivalent piece in the world of metals? He says there is. So our current thinking is along those lines. At any rate, now that the engine has some hours on it (82 to be exact) Mike wants to have the alignment rechecked by yet another diesel mechanic. At that point we can discuss the elbow and see if we can somehow design a system that will let us sleep at night.

So for now, we take it easy with the engine until we can get this issue resolved, again. That’s okay. It just encourages us to raise the sails.

This makes it all worthwhile.

This makes it all worthwhile.

31 thoughts on “Exhaust Elbow Blues, Reprise

  1. I don’t know all the details about this installation so forgive me if I touch a nerve but why isn’t the whole exhaust entirely hose? To be honest I have never seen a setup like what you guys have. I would think high temp exhaust hose would be fine.

    • No need to apologize, Paul. I’m going to pass this on to Mike to reply to your valid question. I’m assuming there actually is a reason why we need the metal piece.

    • Paul,

      I have never seen an entirely rubber exhaust elbow. It is my understanding that until the exhaust gases mix with the cooling water, metal must be used.

      Our elbow is quite high and that height does worry us because the moment arm is greater and therefore exerts greater torsional loads on the joints. But in design, the elbow is not too terribly different than any other high rise elbow. Nigel Calder has a drawing in his excellent Boat Owners Electrical and Mechanical Manual that is fairly similar to what we have.

      • Oh I see now. I should read a little slower I guess. I looked at calders book and I see the design situation you are in. Interesting for us to read about but a pain in the ass for you guys. If i was still at work I’d have a few mech eng’s assigned to it. It may just come down to getting a really good weld and then sleeve it for extra support. Hope you end up with something reliable soon.

        • Thanks, Paul. We will get it sorted. It’s so nice to have the boat home where these things can be attended to more closely. We felt like we were at the mercy of whoever we could find to work with us on a weekend down in Astoria. We did end up with a great mechanic, but he wasn’t in charge of the exhaust installation. Probably we should have had him do that, too. To be sure, when this is over we will know a ton about engine exhaust systems and that’s bound to come in handy some day. Cheers!

    • Good idea. Make the host fraction be as much as possible. Our Catalina 38 had repeated exhaust elbow problems. First, the stainless bolts holding the manifold to the engine sheared not just once but twice, 3 years after the first incidence. We replaced them with much stronger iron. Second, the water injection elbow itself cracked after about 12 years of use. Replaced it with a new elbow and riser pipe. The mechanic at KKMI in Richmond Ca told us in no uncertain terms DO NOT fasten the elbow to any bracket at all, even a bracket to the engine. He said, the entire rig must be strong enough to vibrate on its own. He went on to say that the shorter and lighter the iron and elbow parts and the longer the hose from it, the better. No problems since the big fix two years ago.
      Good luck!

      • Having most of the set up be hose makes sense to me, all other things being equal, because of its shock absorbing qualities. This is a new animal to us as our Cal 34 never had anything like this issue, because the engine was not below the waterline. Thank you for sharing your experience. Catalina 38’s are such good sailing boats. Glad you got your exhaust challenges fixed.

    • Well, we promised to write about all the things that go into making this plan a reality, not just the sunshine and warm beaches stuff. It makes us nervous, too. But we carry on. And it will eventually be worked out.

  2. You really need to support the whole thing better than it is, right now it’s just like a tuning fork that happens to be bolted to something making a variety of vibrational frequencies trying to excite it, which fatigues the attachment points and causes the failure. More weld will reduce the stress and increase the number of cycles before failure, but I wouldn’t think it is enough to get below the fatigue limit (which aluminum doesn’t have, by the way). You could also try adding weights to the tube to try and change its modes away from the frequency of the engine vibration, but I would be inclined to add bracing with dampers to both the engine mounts and surrounding hard points in the boat.

    • I agree. Part of me wants to start all over and see if we can safely lower the height (and the mass). That might mean buying a new muffler that would allow us to lead the exhaust hose fairly. The stock high rise elbow that Beta sells with this engine is only about 6 inches above the mainfold but I had a really crummy angle to the Vetus water muffler.

      The aluminum stock is clearly not sufficient for a long term fix. My preference is to not need any support at all. But if we do end up requiring supports, they will be of steel.

      If you know of a marine diesel mechanic in the Tacoma area that knows her way around an exhaust elbow, send me their name.

      • So not all flexible couplings are rubber, and it looks like off the shelf bellows type systems are available to some extent: http://dmeexpansionjoints.com/diesel-exhaust-flex-assembly-vs-bellows-exhaust-assembly/

        Something like that (the longer the bellows the better) would go between the shaking engine and your stainless U handlebar bit, which would be securely attached to hardpoints on the boat. The key to the bellows coupling is to make sure that the walls are thin enough to allow significant deflection without producing large stresses.

        FWIW, I am a mechanical engineer working on stuff that sits on rockets, if you like I would be happy to set up a time to chat about your situation, at least in theory as I’m not a diesel mechanic. I will send my contact info directly.

        • Thank you for your comment! That is exactly the kind of thing Mike and I were discussing last night and researching all over the web. What did we do before the days of internet? Have to say that I am laughing that you work on rockets because of my previous comment that this stuff shouldn’t have to seem like ‘rocket science’ 🙂 My way of saying that I’m surprised that it appears to be this hard to find a solution to what seems to be a simple enough problem. We may be on the right track with this after all.

    • Do not support the elbow. It needs to be strong enough to vibrate on its own. Support leads to shearing moments more forceful than no support.

  3. sorry to hear of the ongoing exhaust “blues?” The whole unwieldy (unweldy?) contraption that what’s his name cobbled together secretly scared me. My 2 cents? With a ridgid connection to the high vib diesel and that much metal mass, you’ll never have peace of mind Michael. Maybe that’s why mixing elbows are so short to begin with. High temp rubber? Do you have NASA’s phone number? What then? Short stub out off the man flange with a vib absorbing run of exhaust flex ( 6 in or a foot?) then hook up the Astoria tuba. No I don’t believe that heavy thing can ever run in tune w/ the diesel. Maybe a flex pipe just downstream of the maniflod would dampen the vib enuff for the rest of well supported (and soft mounted) metal tubing system to survive. Maybe……
    I probably shouldn’t say this but…… I’d start thinking dry stack.
    good luck. At least things will be easier now that she’s home. Capt. john

    • Yeah, John, I think we’ve had the whole ‘dry stack’ conversation before. Wouldn’t that be nice? We are of one mind on almost everything you’ve said. It just seems so counter intuitive to bring salt water anywhere near your engine. But another time, another boat, right? This is about the rigidity of the connection, as well as the distance and angle between the engine and the water muffler. I’ve been saying ‘more flexible connections’ and not having the right terminology. Perhaps ‘exhaust flex’ is what we need? I think the elbow is worth salvaging and working with if possible, because we do have the issue of the engine being below the waterline. Definitely what we want is to dampen the vibration because I completely agree that it is unlikely that we will ever get the pipe and the engine to vibrate together consistently enough to relax about this issue. Very glad to have you in on this conversation. You know this boat well. We will get this sorted out and are not beaten yet.

      • …………………………………………….which brings up the million dollar question, why the water backed up in the first place? Maybe take a step back and revisit that? Solving that mystery would allow you to use the tried and true mixing elbow, which probably came with that gold plated diesel. After all, neither the old old Volvo nor the old Ford had those issues with the set up you’ll recall from last year. No hi rise, wrapped $3000 custom jobbie. Might have some thing to do with exhaust pressure, volume or both. But definately specfic to the repower. You guys always seem to examine issues thouroughly, thoughtfully, practically and creativly…. you’ll get it right this time w/o the stress of wanting to get it done and leave you know where….
        cheers, capt john

        • Well that IS the million dollar question and we’ve gone over that in our minds only about a zillion times. Of course, the reason you pulled that old engine out in the first place was a ‘water in the oil’ issue that was never actually resolved in terms of why it happened. Clearly you’d run that engine many times with no problem, and the exhaust elbow, which we’ve looked at another million times, is a stock piece. That engine sat higher up in the engine room, and the elbow was placed differently on the engine in relation to the water muffler. Fortunately we are not out anything close to thousands with this piece, more like hundreds. And it is still possible that this piece will work fine once we get the vibration/stress issue fixed. But yes, we will eventually get it right. Don’t worry about that. It will happen. It’s a frustration to be sure, but even if we scratched the whole thing and started over we’d be okay with it.

  4. Boy, this is disappointing. But you know, so many things could go wrong on a boat and at least this one can be fixed somehow. I don’t have any suggestions but I feel your frustration after so much time and money and research was already spent on a “fix”.

    Looking forward to seeing the real solution one day, for now let’s celebrate the engine isn’t flooded.

    • You know, I think we actually have a good attitude about this at this point. Our goal was to get this boat home where we could attend to these things more easily than trying to find someone on a weekend in Astoria. This is just one of those things about boats. Every boat is a little bit different and every system seems to be specific to a specific boat. Fortunately we have contact with the Black Swan owners down in the Bahamas. They have the same boat and have an exhaust elbow that is even higher than ours. The problem with these boats (if you can call it that) is that the waterline is pretty high. We’ll just keep hacking away at this problem until we come up with a good solution, then we’ll get an extra one and keep it on board as back up!

  5. A previous commenter mentioned fatigue failure and noted that aluminum doesn’t have a fatigue limit. In other words, any cyclic stress (i.e. due to the engine vibration) would contribute to fatigue failure. In addition, welding aluminum typically reduces its strength by half.

    On the other hand, and as an idea for an alternative, steel does have a fatigue limit (a stress below which the piece will not fail due to fatigue regardless of number of stress cycles). And its strength is typically not affected by welding. Therefore, I would propose considering steel (stainless, 316L?) rather than aluminum for this application.

    Lastly, if we wanted to get “fancy”, we could estimate the cyclic stress level that was present in the aluminum by estimating the number of stress cycles it experienced before failure (engine RPM x minutes to failure would be starting point). Comparing those number of stress cycles with aluminum’s published fatigue characteristics (particular to the alloy–likely 6062 if an extruded piece), would provide an estimated stress–and then this could be compared with steel’s published fatigue characteristics in order to specify a steel section such that estimated stress was below its fatigue limit. And then you could dump a significant factor of safety on top…and call it a night. That’s not to say some other location wouldn’t be the next to break, but….food for thought.


    • If I’ve followed you at all the bottom line is that steel is better. And we agree that it is. Mike chose aluminum for the supports because we do not have an inverter on the boat and were at anchor in Bellingham. He had his drill, which had one charged battery, and he knew he could work with the aluminum under those conditions. No surprise really that it took the load and busted. No, that was a temporary fix and we knew it. Now that we are in Tacoma, we are looking for someone who knows marine exhaust systems. Frankly this, to me, seems like it should not be rocket science. And yet not every ‘expert’ has given us good advice, as we have seen. To me, it makes more sense for there to be rubberized pieces in the system to take the stress, like the piece that is between the pipe and the water muffler. That protects the pipe and allows it to jiggle without harm on that end. But I understand that the exhaust is too hot for a rubberized piece that close to the engine. There is another boat of this make and model in the Bahamas right now and we are in touch with them about their exhaust system. They, too, have a big piece of tall metal and we are interested in how they supported it. Hopefully they will post a comment here on the blog.

  6. Hi Melissa,

    It sounds to me like you have followed what I was trying to convey with my above comment. Steel is better (except for fabrication difficulties). I would also be interested to hear what the other boat has done–no sense in re-inventing a solution if a solution is known to exist! As for the rubber pieces that dampen vibration and limit deflection (and therefore stress), reduced stress is what it’s all about, so that makes sense to me too. In that regard, anything that reduces stress, whether rubber pieces, thicker material, or additional rigid supports, those would seem to help. In terms of removing the ‘rocket science’, I envision it being simply a matter of “what are the stresses?” and “what is the strength (and, more relevant, what is the fatigue limit strength of the material)?” If stress is greater than strength, then failure will eventually occur. But engineering analysis aside, I think that trusting intuition (you mentioned doubting the fancy new part since the first time you saw it) often leads to an effective answer. I’ll be interested to learn what effective answer you come to!

    BTW, we communicated quite a few months ago while you were in the searching phase, and I’m thrilled that you have found your boat! We found our boat recently as well, a Cal Cruising 35, and are digging into the same enjoyment! Your blog is totally relevant to us and really enjoyable (and informative). Thanks!


    • Yes, I very much remember talking to you when we were both searching for boats! As I recall you, too, were looking for that perfect hull combination of stability and sailing performance. A Cruising Cal 35 is a wonderful boat! So glad you found one and we’d love to see what you do with her. My comment about ‘rocket science’ was not regarding your explanation, but a reflection of my surprise that this has turned out to be so hard a think to fix. I mean, it really does come down to designing something that can withstand the vibrations of the engine and a rigid mount does not seem like the best solution for long term. Most things have a breaking point. I think if I am disappointed about anything it’s that the marine ‘expert’ that designed this wasn’t such an expert at all. Our friend John, who is the previous owner of this boat, mentioned in a comment here that he would be looking at flexible exhaust hose, so we are researching that now. I knew there must be something that would allow flexibility in the system and also be able to withstand the high temps of dry exhaust gasses. Perhaps that will be part of the answer. Glad to have your comments here, Tristan. Many thanks,

  7. Hi guys,
    I took the insulation off our set-up and found a st. steel “bellows”. Tara can send you a photo on FB, if you want. Above that, the fibreglass wrapped part has a couple support struts, screwed to the bulkhead. I’m not sure that’s the best solution, or that it would work for you. It strikes me that cars have a long pipe that hangs on rubber mounts; perhaps you could take the weight off it by mounting to the deckhead with something similar – just look at the exhaust pipe on your car if you can’t visualize what I’m talking about. I’m concerned also about the number of welds in your pipe – and even if the pipe needs to be that heavy. I wonder if a muffler shop would be able to bend up a riser pipe to suit you, without all the welds. Otherwise I think some strengthening webs would need to be welded in where it broke. Good luck.

    • Ah ha! So the steel bellows is what you, too, have. We are definitely onto something here. For our readers who may be reading comments, Black Swan is the same kind of boat as Galapagos. If you can have Tara send photos I would very much appreciate seeing them. It is possible that a muffler shop could have made something with fewer welds, and, in fact, our mechanic had referred us to a muffler shop in Astoria. They never returned Mike’s several calls. Getting people to work on cruising boats in Astoria is much harder than one would imagine. I think we will have an easier time of it now that we are in the Seattle/Tacoma metro area, and in fact one of our readers gave us a referral in a comment. It will all come together. I really appreciate the time you took to unwrap your setup and take a look, and the photos, in advance. Glad you guys are having a terrific time!

  8. What a great read. We love Griffin Bay as well. 12 knots, wow. Exhaust elbow: How can something so simple be so difficult to install? Jeesh. Wish u luck on finding another “mechanic” to “fix” this nagging issue. Maybe you need to find a plumber or exhaust persons.

    • We are of one mind, Al. How can something that seems like it should be fairly straight forward be do complicated? We are wanting to stand back snd take a look at this whole system now that Gslapagos is home. One reader gave us a name of someone in Ballard. We will probably be contActing him.

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  10. Hope you don’t have to rebuild the exhaust piece… but if you do you should have a flange welded on the end and get a standard injection elbow that bolts to that flange. That will make replacing the injection elbow very easy and inexpensive in the future. Looks like you could also make it smaller by reducing the length across the top and using more rubber hose to go to the muffler. Reduces weight and space needed.

    I also agree that mounting the exhaust piece to the bulkhead is the best way and having a flexible hose to the engine. That exhaust piece is a very long heavy lever arm with one end vibrating a lot.

    For insulation check out Ballard Insulation (great stuff, use it on my boat)

    For hose you might try

    For flex hose check out here (I haven’t tried these folks but looks like what you need)

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