Turbo coating with ceramics

Discussion in 'Propulsion' started by Manateeman, Aug 13, 2020.

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  1. Manateeman
    Joined: Oct 2019
    Posts: 40
    Likes: 1, Points: 8
    Location: Kennebunk ME

    Manateeman Junior Member

    Greetings. My boatbuilding is getting slower as I get older so one day I notice my turbo is stuck.
    Yanmar 4LH-DTE. Looked inside. Yikes. Rust city in the hot side. New Turbo. Talked to engineering friends who recommended taking off the exhaust side and bringing it to a specialist who could ceramic coat it. I assume one should not mention commercial names...so hint...lots of car exhaust and guns.
    I ran it for a summer and pulled it off to look. I can’t see any rust. Looks the same.
    Comments?
    Lastly, anyone done this to a propeller?
    Thank you. Mark the manatee.
     
  2. kapnD
    Joined: Jan 2003
    Posts: 692
    Likes: 79, Points: 28, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    The exhaust system design is the usual culprit when rust is present in the turbo.
    the raw water intrusion that causes the rust will eventually find its way into the rear cylinder.
    Ceramic coating of turbo cavities is a popular high performance mod that has little value on a workhorse.
     
  3. Manateeman
    Joined: Oct 2019
    Posts: 40
    Likes: 1, Points: 8
    Location: Kennebunk ME

    Manateeman Junior Member

    Well I’ve been called a horses derrière but I’ve never considered my boat to be a horse. LOL.
    Please let me elaborate on the exhaust design. Downstream of the turbo is a water lift which is followed by a custom gas water separator ...the design very similar to commercial units on small yacht generators. Because I worked for a number of boatbuilders, I got a lot of excellent help with the system. We have a ball valve drain on the water lift and a window so you can see inside the separator. The separator has two drains port and starboard . Sailboat.
    The people who looked at the design and the photos of the actual build are recognized experts in mega yacht exhaust systems. Reviewed by Two gentlemen with advanced engineering degrees and experience in yacht construction.
    So I have to pause when you state rust in the turbo exhaust side is the result of poor exhaust system design.
    It took me a number of years to build the boat and a lot of things I did not exercise every day , including me, got rusty.
    The mixer is stainless but I can’t remember when we changed it but I think it was just after we launched. I guess we have to wait a year or so, but I’m pleased with the ceramic job. Maybe it is of little value to some but I’m pleased even if my yacht is viewed by some as a workhorse...whatever that is.
    Happy trails to you. Mark the manatee.
     
  4. kapnD
    Joined: Jan 2003
    Posts: 692
    Likes: 79, Points: 28, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    Workhorse= your average marine engine as compared to a hot rod motor.
    Maybe you do have a hot rod motor in your sailboat? Makes no difference.
    You have ceramic coated your turbo without determining why it was rusted?
    Bear in mind that any raw water intrusion through the exhaust is an unwelcome visit, with possibly catastrophic consequences extending well beyond a stuck turbo.
    I appreciate the fact that you and your distinguished design team did their homework, but something’s amiss!
    I’m not knocking your boat, or it’s design.
    You posted asking for comment without offering much in the way of specific information, and you got a reply.
     

  5. KeithO
    Joined: Jul 2019
    Posts: 239
    Likes: 37, Points: 28
    Location: Michigan

    KeithO Senior Member

    Assuming that the outlet housing is cast iron (which btw is most likely an alloy to improve its corrosion and strength properties) it is still true that it will "flash rust" very quickly when exposed to atmospheric humidity. It looks like crap, but so long as the corrosion is not in the form of an expanded flaky rust, it has no consequence on the operation of the turbo. The engine is a combustion machine so water is one of the natural products of combustion together with a cocktail of other products in the exhaust including Co, Co2, various HC's and sulphides, nitrides and the various solutions they can form with water. So it is a somewhat corrosive mix, sometimes the HCs and soot can coat the surface and act as a bit of a barrier.

    The clearances on the exhaust side turbine are probably higher than on the compressor side, because the exhaust side has a lot of energy to work with and it needs to use only some to do its job. On the other hand the compressor side is working pretty hard at lower temperatures to compress the air and the tolerances will be closer. But of course that housing is usually aluminum, and its usually a decent grade to resist corrosion (pretty sure some salt fog can get into it).
    So, if it pleases you and you don't mind, then go ahead and get it coated. All that matters is what you think when you look at it. Given what diesels cost in the US, I'm sure we all want our equipment to look great. The turbo is usually a purchased part and the accountants are the ones who decide what it gets to look like.
     
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