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Aft bilge pump lets water in?!

Discussion in 'Cabo Yacht' started by Jrms80, Nov 28, 2015.

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  1. Jrms80

    Jrms80 Member

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    Ive been searching for a mystery leak and finally found it. When the boat comes off/on plane the aft bildge pump discharge hole goes below the water line and about two quarts of water come bubbling out of the pump itself. My question is what's broken? Is the pump itself a check valve or should there be a separate one installed? If I need to install a check valve what's the best location? At the pump or at the discharge?

    Thanks, Joe
  2. K1W1

    K1W1 Senior Member

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    Can you put a loop in the discharge line to perform the task that will eliminate the chance of any non return valve failing in the future. A rubber flap on the outside will also help to stop water getting pushed back up the pipe.
  3. RER

    RER Senior Member

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    As a rule I don't like to use a check valve on bilge pump discharge lines. They can get sticky. A loop above the waterline is best. Sometimes that can be difficult in a smaller sportfisher lazarette when there's limited space below cockpit deck. However I've seen where a loop is missing simply because the hose was too short. In my experience a rubber flap only helps when backing down on a fish.
  4. Capt Ralph

    Capt Ralph Senior Member

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    Please ad to these thoughts; a vented loop.
    You can get a tighter radi on the 180 bend without the hose crushing. Removes the attempt of siphoning.

    I know Sleze Rays use Whale (& Like) rubber check valves and dump into a common manifold eventually dumping astern.
    On one boat I removed these check valves and installed high vented loops and direct discharge. The remaining bilge water stayed lower and less frequent pump operation when off shore.

    When dockside or anchor, A low volume, low pickup (diaphragm) pumps that last 1/2 to 3/4 inch of water.
    Last edited: Nov 28, 2015
  5. Jrms80

    Jrms80 Member

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    What I'm wondering is how CABO could have sold this boat new? If I had bought this expensive boat and took it for a sea trial and the bildge went from dry to having water in it I'd want it fixed. Why bother putting on it these expensive "dripless shaft seals" if your gonna allow a gallon of water to dump in through the aft bilge pump when the discharge hole goes under water? Am I wrong for even caring?

    I'm not sure there is enough room between the top of the through hull discharge and the top of the stern to put a loop high enough to keep the water out. If not I'm left with some sort of check valve which is problematic due to a potential failure in the closed position. I do have 2 other pumps on a different outlet and the "crash" pump so really I'm not overly concerned.

    Thanks to all for listening/helping with my new boat issues these past several weeks. Call me crazy but I'm enjoying working through all these somewhat minor boat issues. Helps keep my mind off all the real problems in the world.




  6. Beau

    Beau Senior Member

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    What I'm wondering is how CABO could have sold this boat new

    Good question. Was this factory rigged? What do your schematics show?
    Maybe a new thru hull location is in order? I'm assuming the fitting now comes thru the transom. Maybe it needs to be higher or side mounted. I assume when you accelerate, no water enters, its when you come off plane?​
  7. Capt Ralph

    Capt Ralph Senior Member

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    I'm not sure there is enough room between the top of the through hull discharge and the top of the stern to put a loop high enough to keep the water out.
    It takes one beer and a flash light to determine the answer here.

    Maybe a new thru hull location is in order?
    Beau beat me to it; Relocate the discharge if the loop idea does not pan out.
  8. Jrms80

    Jrms80 Member

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    Exactly, there are two low and aft (3 inches above water line) molded right into the gel coat holes. There very nicely done and hidden in the black bottom paint. The one on the port side goes to the aft bilge. The starboard one goes to the fish box macerater pump. That pump is built different and won't allow water in like the bildge pump or they both would have water coming in.

    I can only assume this is the factory install maybe someone who knows these boats can shed more light on it. Not a big deal to me now that I know what it is.
  9. Beau

    Beau Senior Member

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    Not a big deal to me now that I know what it is.

    IMO , it is something you should fix in some manner. Not a good idea that sea water can get into your bilge thru that fitting. You describe these thru hulls to be located in the area of bottom paint along the transom, so when you say "3 inches above the water line", do you mean above the outside water surface or above the water line painted on the hull? If the former, I would definitely get that looked into. That sounds like an open seaway if she squats at the dock for some reason
    Last edited: Nov 28, 2015
  10. Capt Ralph

    Capt Ralph Senior Member

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    Or maybe the original pump was a low volume diaphragm par pump?
    Is there a forward high volume pump that would clear water also?
  11. Jrms80

    Jrms80 Member

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    Don't misunderstand me, I will fix it. It's that's this now known problem is a small one imo.

    Here's what I'm thinking will work for me. I'm gonna buy a PVC T shut off valve and plumb it high into the hose. Part of pre/post flight of the boat will be to open/close the T. When I leave the boat at the slip I'll open it, before getting underway it gets closed.

    Worst case if underway and I forget I'll get water in the bildge. Worst case at dock and I forget to open it I'll have to rely on the two remaining bildge pumps to keep up with a leak that had to happen during the time between my boat visits. A several things need to go wrong and be missed before that's a serious problem. Seems like acceptable risk to me either way, but I understand it's not a perfect solution.
  12. Jrms80

    Jrms80 Member

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    Yes 3 separate bildge pumps but only 2 discharge points. Aft bildge is alone, mid and forward are plumbed to a mid ships higher discharge point.
  13. Capt Ralph

    Capt Ralph Senior Member

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    You have been talking to Buba..
    I can sense the banjo music coming thru the forum.
  14. Beau

    Beau Senior Member

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    Interesting, the two forward pumps use the same discharge, which means the two pump discharge hoses are T or Y connected somewhere. Rcrapps, what do you thing of that set up for the possible recycling of the bilge water. JRM, usually one pump of the 3 will be the dominant pump at the dock. Is that true of your boat? If so which one is it? If it's the rear, I would recommend against that T valve - you forget to open that under your plan and you might be looking down at your boat after a heavy rain.
    Last edited: Nov 28, 2015
  15. Jrms80

    Jrms80 Member

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    First pump to activate at the dock in a heavy rain or leak is the most forward pump in the cabin deep V bilge followed by mid only then if water keeps rising the aft pump would start. Underway the opposite happens. I would see the amber helm pump "on"light if the aft bilge activate and investigate if underway with or without the T valve closed. I can live with the at the dock risk with the remaining two pumps.

    I think it's way overkill to drill a new hole in the boat to try and fix this problem. My solution prevents an unknown stuck check valve from causing a problem. I live by check lists in my day job so I understand the importance of doing them.

    Thanks for the laugh with bubba and his banjo! Really I don't think my solution is half bad!
  16. Capt Ralph

    Capt Ralph Senior Member

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    which means the two pump discharge hoses are T or Y connected somewhere. Rcrapps, what do you thing of that set up for the possible recycling of the bilge water.
    Y connect with nice tall vented loops could be o k, Not preferred. Connected into a drain manifold would be a step up (not much) if loops were still maintained.

    I'm wondering if this stern discharge was another bait/fish box drain originally.

    Were getting close to a thread on these same comments not so long ago.

    I would still advise on fixing the stern pump issue with a correct loop or relocating the discharge properly.
    PVC and discharge valve are not a fix.
    This would fail every code. Would fail any survey. Would probably
    disrupt any insurance claim, even if not an aft de-watering claim.



    Humor is a must in these threads, Thank you for taking it lightly.
  17. Capt J

    Capt J Senior Member

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    DO NOT DO THIS. Just put a check valve at the pump. If you're running at cruise all day and start taking on water, it is all going to run aft, and you could end up with a sinking situation with 100's of gallons back there before it ran to a foward pump. Having this pvc valve closed will kill the bilge pump if it kicks on and cannot pump anything, and then you have big issues. Just put a check valve right at the bilge pump. I can't remember if the 35's had one from the factory. You can run a vented or non vented loop up the gunnel, either foward or aft of the rod lockers on the hull side as well. or inside the transom on either side of the livewell.
  18. Jrms80

    Jrms80 Member

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    Even though I've owned boats for 30+ years this is my first deisil and my first non trailer-boat. So I certainly appreciate all the knowledgable input and understand there is much I don't know. So what is a diaphragm bilge pump? Does it have a built in check valve? Also Capt J, did CABO build its 31 express boats with this problem? So you think their factory fix was a check valve? Honestly I liked my T valve idea but after reading these posts I'm ok with the check valve. Frankly it's an easier fix anyway. I appreciate all the advice!
  19. RER

    RER Senior Member

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    The shutoff is a terrible idea - It's just not a viable option. And PVC is a no-go below the waterline.

    I posted 'as a rule' I don't like check valves on bilge pumps. However in some cases it's better than than the alternatives. Like in this case.
  20. Capt J

    Capt J Senior Member

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    I've run several hundred Cabo's over the years, but never a 31. The 31' was their first boat and not sure if it origionally did have a check valve, but I'd put one.

    A Diaprahgm bilge pump would be similar to a Whale gulper, etc. It can run dry and you can use a low profile pickup to get more of the bilge water out. I wouldn't worry about it and just fix the Rule that you have with a check valve 6-12" from the bilge pump.