Wet exhaust hose overheating

Discussion in 'Diesel Engines' started by Andy Muir, Jun 6, 2018.

  1. Andy Muir
    Joined: Jun 2018
    Posts: 5
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    Location: Kinsale Ireland

    Andy Muir Junior Member

    Hi
    I have a 17 year old Trader 485 with twin Perkins 225 diesels. Engine reliability has been good until the hose between the wet elbow and the fiberglass exhaust burst, filling the engine room with fumes. As the hose was probably the original I put it down to wear and tear and just replaced it. But it is getting much too hot. Last time out it was smoking and I've just taken it off and the new hose is now burned and cracked on the inside. There is also signs of burning the top end of the fiberglass exhaust where the water from the elbow should cool it.
    Both engines run fine and both exhaust installations are basically the same. Where the cooling water leaves the engine it is split 3 ways; prop shaft bearing, wet elbow and muffler. The connections to the bearing and the muffler rise above the connection to the wet elbow by perhaps 200mm.
    Impellor seems in good condition, strainer is clean and water leaves both exhausts in about the same quantity. But the hose on one engine is getting too hot.
    Any ideas where to look?
    Thanks
     

    Attached Files:

  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If you disconnect the hose feeding the wet elbow and there is good water flow, then the elbow is most likely clogged or closed by corrosion.
     
  3. Andy Muir
    Joined: Jun 2018
    Posts: 5
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    Location: Kinsale Ireland

    Andy Muir Junior Member

    Hi Gonzo
    Thanks for the quick reply. As it happens I took the exhaust riser off a few minutes ago. I put it on the dock and ran a hose into the water inlet. Everything is very free flowing. With about 100 mm of head on the water inlet it is taking the hose on full bore. If anything I''m wondering if it's too open as water sprays (albeit lazily) from the lower openings but at the top just trickles out. I'll try to run a second hose into the inlet and see if that helps.
    I ran the engine very briefly with the hose disconnected and there seemed to be plenty of water available - salt water all over everything!
    Do you know why the engine cooling is split 3 ways? I understand the feed to the bearing but why split the water to the exhaust between the muffler and the elbow?
    Is there any chance the bearing is taking too much water?
    Thanks again.
    Andy
     
  4. Andy Muir
    Joined: Jun 2018
    Posts: 5
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    Location: Kinsale Ireland

    Andy Muir Junior Member

    I just ran out a second hose. The two hoses are just pushed into the water inlet hose, not sealed. The elbow is easily flowing all the water with only about 100mm head.
    The flow out of the elbow still looks a bit lazy, I was expecting jets rather than water just pouring out? New picture attached.
     

    Attached Files:

  5. Andy Muir
    Joined: Jun 2018
    Posts: 5
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    Location: Kinsale Ireland

    Andy Muir Junior Member

    Another update: I put the riser back on without the hose and temporarily blocked the water feeds to the muffler and the prop shaft seal. There was vigorous water squirting out of the elbow along with all the fumes. This looked promising so I refitted the hose, leaving the other two line plugged. I only ran for 30 seconds or so as there were fumes coming from the back of the boat but zero water!
    I'm completely stumped!
     
  6. Andy Muir
    Joined: Jun 2018
    Posts: 5
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    Location: Kinsale Ireland

    Andy Muir Junior Member

    Last update for today: If I run as above but use a hose to supply water to the feed to the muffler everything seems to work. So there must be something inside the muffler that need a separate water supply to allow water out? Seems nuts but that's what I have so far.

    Has anyone experience of a muffler that needs a direct water feed?

    Thanks
    Andy
     
  7. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    Hi Andy and welcome to this forum! Check that there is no restriction in the pipe to (and into) the muffler. If there is an increased resistance, the water that should have gone to the elbow will flow into the muffler and/or shaft bearing. My first guess is that a loose strip of burnt inner lining from the old rubber hose is stuck somewhere in the muffler inlet (but before the muffler water inlet) and increasing the exhaust pressure in the elbow. As a consequence, the "elbow cooling water" is diverted to a low-pressure branch.
     
  8. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    That sounds like a possibility
     
  9. Lepke
    Joined: Sep 2015
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    Location: Oregon to Alaska

    Lepke Junior Member

    Common on bigger engines with high volume raw water pumps is a split that sends some water overboard so the muffler doesn't have too much water. My Detroit mains split off before the elbow and the direct over-the-side water is controlled by a valve. The more closed the valve, the greater the water supply to the exhaust. In front of the valve is the line to the shaft bearing.
     

  10. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Perkins is famous for its cast iron exhaust manifold and exhaust elbow failures.
    If you have this setup, the manifold could be plugged up preventing adequate water flow to the elbow.
    Then there’s the infamous “fix” on newer models which was the manicooler, another brain fart.
    If there’s adequate water flow to the exhaust elbow, try plugging some of the bottom holes to help cool the top of the piece.
    Post some pictures so we can see what you’ve got.
     
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