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Strange engine part phenomenon

Discussion in 'Ask All Sailors' started by Mark Maulden, Feb 8, 2019. Add this thread to a FAQ

  1. Mark Maulden

    Mark Maulden

    Joined Jan 25, 2011
    1,873 posts, 208 likes
    S2 11.0A
    US Anacortes, WA
    47D869B4-B5AF-4F8B-B50E-C28EAE69F45B.jpeg F15684DF-7876-4CE7-A845-06D0CE4583CD.jpeg 47D869B4-B5AF-4F8B-B50E-C28EAE69F45B.jpeg This an engine thing but I decided to post here. Most of you might remember that I ditched my Volvo MD17 a year ago and replaced with a Beta. When I did that, I saved a lot of the Volvo stuff to sell on CL or ebay. So, a lot of the Volvo stuff resided in boxes in my shop and garage for the last year. I have been slowly selling stuff off. Slowly...Four days ago, I started going through what I have and looking what has been selling on ebay. I have two exhaust elbows. One from my boat and one from an acquaintace’s boat..I was going to list my elbow and when I looked at it, it was was not cracked three days ago and it has been sitting in a heated shop for a year since it was taken off the boat. Strange.. F15684DF-7876-4CE7-A845-06D0CE4583CD.jpeg 47D869B4-B5AF-4F8B-B50E-C28EAE69F45B.jpeg 47D869B4-B5AF-4F8B-B50E-C28EAE69F45B.jpeg

  2. uncledom


    Joined Jun 11, 2011
    1,130 posts, 243 likes
    Hunter 41
    US Lewes
    just from the rust streak that is part of the crack I find that impossible.

  3. garymalmgren


    Joined May 29, 2018
    57 posts, 41 likes
    Canel 25 foot
    Jonathan jp Shoigama, japan
    Hmm. Not much chance of selling that.
    So much for the quality of genuine parts.

  4. sailnoproblem


    Joined Oct 10, 2011
    478 posts, 142 likes
    Tartan 34C
    US Toms River, New Jersey
    That crack has been there for quite awhile.

  5. jssailem


    Joined Oct 22, 2014
    8,748 posts, 3,746 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    :yikes: It was time to retire that part.

  6. Skipper


    Joined Oct 9, 2008
    1,665 posts, 306 likes
    Bristol 29.9
    US Dana Point
    Do you know anyone in your neighborhood who has a Volvo engine, who also knows that you have Volvo exhaust elbows in your garage?

    Satori and Tom J like this.
  7. capta


    Joined Jun 4, 2009
    3,006 posts, 1,075 likes
    Pearson 530
    na Admiralty Bay, Bequia SVG
    If the hole was round, I'd probably blame cockroaches.
    However, considering the rust, I think there has been a hairline crack (perhaps a casting flaw) for quite some time that may have even leaked a bit when warm and being used on the engine. Perhaps the shop just got warm enough that the crack expanded the full length of the casting flaw? A bit of duct tape and you should be good. People will buy ANYTHING on Ebay as witnessed by things like the Virgin Mary grilled cheese that sold on eBay for $28,000 back in 2004 and its knock off Jesus toast, along with a Corn Flake in the shape of Illinois that sold for $1,350.

    AlexB likes this.
  8. Benny17441


    Joined May 24, 2004
    5,679 posts, 399 likes
    CC 30
    US South Florida
    That crack has been there for a while. Look for another reason; the elbow fairy?

  9. Tom J

    Tom J

    Joined Sep 30, 2008
    1,365 posts, 264 likes
    Catalina 310
    US Quincy, MA
    Lol. That's what I was thinking. We used to call that "Midnight Auto Parts".

  10. carlpaez


    Joined Sep 9, 2009
    3 posts, 1 likes
    Pearson P-26
    US Dana Point
    While I am not familiar with the specific material used on the Volvo engine, I can tell you that there are certain materials which are know to suffer from "stress corrosion cracking". I learned that when I was working as a structural engineer on the Lunar Module (1968) at Grumman Aerospace Corp in Long Island , NY. We had LM 3 in the clean room (no possible corrosion there), yet a part installed in the Aft Equipment Bay was found cracked. I got all excited and phoned my boss (on a Sunday). He calmed me down and explained it was a new phenomenon just discovered in certain metals. If when they are fabricated, or installed and the part is under a constant tension stress, then a small crack will develop and the part will eventually crack (fail) with no other load on it. Aluminum 7075-T651 and other types of alloys that are very susceptible to stress corrosion cracking. So, it could be that the Volvo part was casted (made) with a residual tension stress in it (possibly during cooling), so it just took a long time (not loading) to crack it. For more information go to the Internet and type "stress corrosion cracking" and you may get a mouth full of information on the phenomena. We in the aerospace industry have learned what to avoid it in terms of material and alloys, but also in preventing "clamp-up" which leaves a tension residual on certain parts when they are attached on a not smooth surface.

    Last edited: Feb 11, 2019
    Tom J likes this.
  11. TimFromLI


    Joined Jan 7, 2014
    32 posts, 7 likes
    Beneteau 45F5
    51551 US Port Jefferson
    Could it be Hydrogen embrittlement? The bolt in the "cheese grater" building in London were popping off do to stress cracks caused by this. It happens in very hard steel. "single atoms of hydrogen enter the steel, migrate through the crystal lattice, and are attracted to the areas of highest stress. Here they cause tiny fractures to propagate and, in a worst-case scenario, a cascading effect can take place, as the stress increases and attracts more free hydrogen, leading to a sudden catastrophic failure"

  12. Mark Maulden

    Mark Maulden

    Joined Jan 25, 2011
    1,873 posts, 208 likes
    S2 11.0A
    US Anacortes, WA
    This part is heavy cast iron. I inspected it very closely several days before I noticed the crack. It has never leaked in service. I would have noticed if it did. Strange that it would decide to crack after a year of being on the shelf...

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