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Lasdrop Shaft Seal Failure

Discussion in 'Props, Shafts & Seals' started by DOCKMASTER, Jun 3, 2021.

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  1. DOCKMASTER

    DOCKMASTER Senior Member

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    How do others have their seals plumbed? Tee lines or crossovers? Perhaps most others have a single port so you just tee them together?
  2. mapism

    mapism Senior Member

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    What I would do at next haul-out is replace both with some seals not built by amateurs.
    In fact, I can only see two alternatives: either they don't have a clue and are making up the overheating excuse (why one side only, for instance?), or they totally failed the very basic duty to provide some decent instructions.
    Both ways, I'd rather have stuffing boxes on my boat than anything built by these folks.
  3. Donzi 54

    Donzi 54 Member

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    Mine are supplied direct from each engine and just have a crossover. Never had a issue with this set up. That is how they stated it should be plumbed.
  4. DOCKMASTER

    DOCKMASTER Senior Member

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    Lew - what brand seals are you running?

    My previous seals were plumbed the same way and I never had an issue either. I'm already seeing signs that the new port seal is failing again. I've got something weird happening here. And I don't have faith in these Lasdrop seals. Although the starboard side has been fine so I'm not really sure what's going on here; yet. You can the port seal bleeding some rust and some black carbon coming off of it. You can't tell from the picture but it is discolored like the other one was that failed.
    It pisses me off that I've had to haul and replace seals, especially given they provided zero guidance on how to plumb these **** things. Here's current photos taken yesterday of both seals.

    Stbd Seal 9-921.jpg Port Seal 9-9-21.jpg .
  5. d_meister

    d_meister Senior Member

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    When I first was involved with dripless seals, the info at time of installation was that the reason for the forced water was that at speed, the cavity behind the seal would accumulate air (like station-wagon effect) and the seals would overheat. The purpose of the forced water was to eliminate air and allow heat transfer with water.
    On the last yacht I was running, it had PSS seals with plumbing from one engine only to each seal. While maintaining engine zincs, I found that the last heat exchanger in the starboard engine raw water circuit always had sea water in it well above the water level outside the boat. Since it made a situation requiring clean up, I explored the raw water circuit and found that the nylon hose nipple at the PSS seal was completely shut with salt! The yacht was on a dockside run schedule that I performed every two weeks (when not underway), and yet it clogged.
    Something else to explore is the possibility that the low pressure zone in the seal is drawing air from the plumbing itself. Perhaps a tee with a petcock or a flow meter sender in the cooling lines could be installed to verify that there is positive water pressure at speed.
    Another issue is that the hose barbs should be at the top of the seal, as in the case of your starboard seal, there is potential for an air pocket at the top of the cavity.
  6. DOCKMASTER

    DOCKMASTER Senior Member

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    We pulled the hose off the seal coming from the engine and fired them up and there is significant flow going to the seal. We also verified no plugs, obstructions or kinks in the lines. To your point d_meister, we could be getting some type of air pocket or weird pressure differential through that crossover line that is causing an issue for the port seal. What I can't understand though is when we replaced the seal a few months ago we went out and trialed at cruise speed for well over an hour and monitored both seal with a temp gun. There was less than 1 degree difference between them the whole time.
  7. Donzi 54

    Donzi 54 Member

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    We have Tides dripless with multiple spare seals on the shafts. Previous boat had PSS seals and they were set up the same way.
  8. DOCKMASTER

    DOCKMASTER Senior Member

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    I was just looking at the Tides online. They even show them plumbed with a crossover line right online. My first glance through their catalog and I did not see the size I need which is 2.75" shaft and 5.00" stern tube.
  9. Capt Ralph

    Capt Ralph Senior Member

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    Interesting video.
    They keep mentioning to refer to the manual for instructions on the plumbing setup.
    Also, Please listen in on the audio starting @ 1:40.
    "quality components that won't fail".
    Sounds like a verbal warranty to me..

  10. C team

    C team Senior Member

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    That is how my PSS seals are plumbed too.
  11. mapism

    mapism Senior Member

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    I can certainly see why.
    I already posted my suggestion on what I have good reasons to consider the best shaft seals money can buy in this previous post.

    You might be interested to check it out, because the product I mentioned there is military grade stuff, supposed to withstand 5000+ hours with zero maintenance, built in a way (bronze and s/steel only, with no rubber parts at all) that makes those Lasdrop things look like a practical joke in comparison.

    There's just a caveat (aside from not being able to tell you anything about availability and support in the US - let alone in AK): they are NOT designed to be installed directly on a stern tube, but rather on a specific flange resined together with it.
    So, looking at your photos, I guess they would require some adaptation.
    Maybe nothing major, and possibly trivial for someone familiar with GRP, but I just can't tell for sure.
  12. DOCKMASTER

    DOCKMASTER Senior Member

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    The PSS seals look like they have only one port on each seal. Are you saying you have Tee fitting in each supply line going to the other side?
  13. DOCKMASTER

    DOCKMASTER Senior Member

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    I had some flow testing done today. The straight supply to the seal from one engine is about 2 gpm. With one engine running, the supply to the opposite side seal is much, much less. So it sounds like this crossover plumbing is NFG. The only thing I still don't understand is why the port seal is failing. Since replacing it I have never ran on just the Stbd engine. I have run either both engines while cruising and did about 5 hrs. of trolling but that was with the port engine running. So why didn't the stbd side seal fail then and not the port side?
  14. Capt J

    Capt J Senior Member

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    Yeah, I've seen them T'ed. Check your shaft tube, the rust stain is odd, could it be possible that the shaft tube is clogged?
  15. DOCKMASTER

    DOCKMASTER Senior Member

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    I don’t think the tube is clogged. We checked it when we replaced the seal and it was clear. But that being said I’m not taking anything for granted so we are working on a flow test to verify we have clear flow through both sides.
    The rust is odd to me too. Lasdrop claims when the stainless overheats it losses some of its anti-corrosive properties. Now I’m no metallurgist but in my line of work we weld stainless every day. The heat from welding (much greater than a seal getting hot) doesn’t alter stainless properties and make it rust.
  16. mapism

    mapism Senior Member

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    Hence the first of the two alternative possibilities in my previous post #42.
    Which 'fiuaskme is hands down the more likely.
  17. C team

    C team Senior Member

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    Yes, each seal has it's own dedicated supply with a cross over T to supply from the opposite side in case of running back in on one motor. I will take pictures later today when I'm back down on the boat.
  18. DOCKMASTER

    DOCKMASTER Senior Member

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    Thanks but I’m not going to add flanges to my shaft logs or buy seals that are not readily available and serviceable in the U.S. There are easier options for me should I decide to change make and model.
  19. DOCKMASTER

    DOCKMASTER Senior Member

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    Much appreciated!
  20. C team

    C team Senior Member

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    Trying to upload a picture but keep getting too large. I'm resizing but still having the issue.