Nearly sank my boat yesterday.

Discussion in 'General Conversation' started by Bach Wilson, Jun 30, 2020 at 6:47 AM.

  1. Bach Wilson

    Bach Wilson Member

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    I have a 246 diesel. Yesterday the water impeller failed, nearly taking out the whole boat. Luckily we were just departing from home and had just gotten on plane when I noticed billowing white smoke coming out the back. Did a quick shutdown and found all gauges to be normal. Popped the engine cover open and found the exhaust tube to have a hole melted through it just behind the elbow. It appeared to be burning inside. I hosed it down with the wash-down pump through the hole and the smoke seemed to stop. We deployed the trolling motor and slowly made our way back to the dock.

    Once on the dock I started taking a close look. I found the bilge pump was cycling on a few times and there was a leak at the exhaust tip at the stern. I lifted it out of the water and started taking things apart. When I removed the exhaust tube from the elbow, the tube fell out of position and literally fell off the exhaust tip on the back. The exhaust tip had deformed/shrunk so much that the clamps on either side of it were useless. If the arrangement of the exhaust hose wasn't just right, it would have easily fallen apart while on the water. That would have been a big challenge to overcome.

    I am upgrading it all to a silicon tube and a 4” stainless exhaust tip. This plastic stuff below the water line is a real joke. The impeller by the way was 2 years old according to previous owner. Im not gonna take a chance on that part again. The day before yesterday we were offshore all day.
     
  2. Fish Witch

    Fish Witch Well-Known Member

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    Good to hear you got her out of the water quickly before things really went south. Your engine instruments obviously didn't help warn you early enough. A flow sensor on the seawater system is a good bit of insurance. My Yanmar has one on the inlet to the intercooler so you might look to see if you could install one. I like to see my exhaust water flow but with our Shamrock's exhaust below the water line it's difficult to get a good visual so the flow sensor helps. Let us know what you find when you take your SW pump apart. You may need to chase down pieces of impeller to clean out the debris.
     
  3. Mistress

    Mistress Well-Known Member

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    Yikes. I've melted a couple rubber exhaust hoses. Once on the 17' from installing the seawater pump backward an once on the Mack from loosing the key that drives the impeller. They can look fine from the outside, but delaminate on the inside.

    Both boats were all rubber hose with no fiberglass, metal tubing, etc.

    Kinda surprised there was that much heat back out the exhaust tip.

    Not sure the silicon will save much if it melted the exhaust tip. I've usually seen it installed close to the manifolds though.
     
  4. crhodes

    crhodes Well-Known Member

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    I keep a couple of nerf-like footballs on board in case I have to stuff them in the exhaust flanges. Know they work because I've changed out my exhaust pipes with them installed. Just a thought.
     
  5. Mistress

    Mistress Well-Known Member

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    Worst Marine has a big foam stepped cone. Fit about any rec sized thruhull. Replaced a section of exhaust with the boat in the water.
     
  6. Bach Wilson

    Bach Wilson Member

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    The impeller had only one vane remaining. At this point 2 are still MIA. A new OEM impeller is now installed.

    The hose dealer said this stuff will pretty much not burn even when exposed to fire.

    Still trying to find the best fit for a new exhaust tip. Im wondering if a baffled one would do anything for noise? Most of the loudness is engine noise and not exhaust. But killing any of the noise would be nice.

    I will buy a plug for these no doubt. I will also go ahead and replace the floor drain plumbing while in there.
     
  7. Pequod

    Pequod Well-Known Member

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    Definitely locate the remaining impeller pieces.
     
  8. tuner

    tuner Well-Known Member

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  9. Mistress

    Mistress Well-Known Member

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    I don't think they'll burn in the classic sense until there's an actual fire. But they will delaminate, get weak and possibly burst or choke off exhaust. It can take cycles after the original heating.
     
  10. quickstep192

    quickstep192 Well-Known Member

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    I never got around to it, but I was thinking about putting a water flow detector downstream from the raw water pump and rigging it to an alarm. Then I'd have two alarms going off before starting the boat!
     

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