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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. mapism

    mapism Senior Member

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    A discharge under the w/line for a bilge pump is a silly installation, which I wouldn't expect from any respectable builder.
    Did you ever see that on a Cabo?
  2. Capt J

    Capt J Senior Member

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    The aft bilge pump on most every SF exits just forward of the stern and just above the water line on the hull side. Due to the running characteristics of a SF at trolling speed and higher trolling speeds and loaded down with fuel, ice, bait, rods, livewell and trolling some can become under water underway. Most are just above the waterline a few inches while at rest, otherwise you'd have no way to change the hose on the discharge fitting and such due to the cockpit floor covering it if they put it higher. When backing down on a fish, many captains will even flood the entire cockpit of the SF. I'm not just talking about Cabo here but most SF builders. On the lazarette pump I would like to always see a check valve on a SF.
  3. mapism

    mapism Senior Member

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    All well and good, but that's something different from having an u/w discharge - as often happens for the genset for instance, for noise reasons that don't make any sense with bilge pumps.
    Anyhow, I'd rather not have valves on the discharge line (as also others said) on any boat, regardless of how prone they can be to sea water backpressure.
    If anything, on a boat where for whatever reason is impossible to install a high enough loop to prevent backflow, I'd expect the builder to fit a good diaphragm pump that doesn't need any valve.
    Also because most submersible pumps from the usual suspects like Rule, Jabsco, etc. are only mediocre at best, anyway.
  4. Capt Ralph

    Capt Ralph Senior Member

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    I'm starting to notice some trends on the forum, a question is asked and we all try to help, the OP never comments again.
    Bad breath, Poor dress code?
    What's up?

    ie; This re-opened 7 year old thread and the NFG on those transfer relays in another post..
  5. Capt Maritime

    Capt Maritime Member

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    My aft bilge pumps have a loop and then they discharge via a 'Y' with the fish box macerator pumps - port and stbd respectively. The discharge fittings are in the boot stripe which at rest is above the waterline. In theory, when running in rough seas the water pressure could overcome the loop and that shot of sea water could run back through the pump and end up in the bilge.


    Cabo port aft bilge pump discharge loop.jpg Cabo port aft bilge pump discharge.jpg
  6. mapism

    mapism Senior Member

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    Whenever you find sea water in the bilge, do you also find some in the fish box?
    With that arrangement, if sea water runs back into the bilge but not in the fish box, the only plausible reason is that the macerator pumps restrict the backflow. So, you could just replace the current rule bilge pump with a similar one.
  7. Capt Ralph

    Capt Ralph Senior Member

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    In your left picture, is that a leak from your trim tab?
    In-between those just long enough screws?
    Is one of those screws in the hose?

    Was this a left coast or east coast built boat?

    Could it be time to get a set of eyes down there,
    back-down and maneuver some to make the leak happen real time, see where the water is coming from?
  8. Capt Maritime

    Capt Maritime Member

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    No water in either fish box. Those macerator pumps restrict back flow. The Rule bilge pumps do not. No that is not the trim tab hydraulic line, its a Morse type push pull type cable for the live well dump valve. Those long screws fasten the dump valve flange and are much to long, however no they are not penetrating the bilge pump discharge hose. They will be changed.

    Cabo's are built in California - this is a 2005 hull.

    See attached photo of the fish box macerator and bilge pump discharge fitting in the stbd boot stripe. Approximately 5" above the waterline.

    Yes it is time to climb around down there maneuver the vessel/back down and find out where the water is coming from. Keep in mind it is not much water each time - not even enough to kick the pump on.

    Stbd fish box discharge.jpg
  9. Capt Ralph

    Capt Ralph Senior Member

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    Sadly, the later Cabo's were built, not built, built, then scraped by Hatteras and the new Hatteras corp.

    Why I had to ask, We know the left coast builds were pretty well made. One of our YF members made them.
    Wish I remembered his handle, I'd invite him to comment.

    Yep, time for a bilge monkey.
  10. mapism

    mapism Senior Member

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    Precisely what I meant.
    The only real reason for not using one of those macerator pumps also for the bilge is that the Rule thing is cheaper.
    So, you could save yourself the hassle of finding another workaround, and just replace it with a macerator pump, job done.

    BTW, I suppose you must have some other Rule submersible bilge pumps elsewhere, so you could just keep it as a spare.
    Using it to replace a faulty one will only be a matter of when, not if...

    As an aside, instead of replacing those two self-tapping screws with shorter ones, considering that you can reach them, I'd replace them with bolts.
  11. Capt J

    Capt J Senior Member

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    NO, the real reason for not using a macerator pump for a bilge pump is they simply do not pump enough water. A Rule 2000 generally pumps 2-3X what a Diaphram pump does and a 3800 RULE more like 6 x. That's the reason.
  12. mapism

    mapism Senior Member

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    Why, haven't you ever seen a diaphragm pump capable of 2000 gph?
    When I suggested to replace the Rule with one of those, I meant one of that type, not the exact same model/size used for the fish box, obviously.
  13. leeky

    leeky Senior Member

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    It "sounds" like you are referring to YF member MBY, who now is associated with Mag Bay Yachts.
  14. Capt Ralph

    Capt Ralph Senior Member

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    Yep, Thank you our friend.

    OP, there is your original build expert. Private Mail MBY. Ask him to join us on this thread.
    Last edited: Nov 27, 2022
  15. Capt Ralph

    Capt Ralph Senior Member

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    A marine (small boat <20M), bilge diaphragm pump, 2000GPH? Please post such a device.
  16. Capt Maritime

    Capt Maritime Member

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    My Cabo 40 has two 2000 GPH Rule bilge pumps on floats and a high water alarm. One discharges to stbd the other to port. Good redundancy and a good pumping volume when needed. Bilge monkey investigation next underway trip.

    Aft bilge pumps.jpg
  17. Capt J

    Capt J Senior Member

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    Yeah, they're massive in size and not going to fit where a rule 2000 fits.
  18. Capt Ralph

    Capt Ralph Senior Member

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    Problem is, per your picture, on that pad, there may always be 1/2" to 3/4" of water back there.
    Those Rule pumps are not capable of picking up low water.
    And that pad has them higher than the bilge skin.

    I can see in your picture the redundancy.
    The second pump will only come on if the first pump fails, then the high water alarm to let you know the second pump is not making it, then you know there is a problem.
    IMO, a little late by that time.
    I would hope an alarm is sounding when that second pump comes on, then a second (louder siren) sounds when that high water float trips.
  19. SplashFl

    SplashFl Active Member

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    It may "work for you," however if she ever sinks at the dock, will it "work" for the insurance company or give them amo for not paying off a claim.
  20. CaboFly

    CaboFly Member

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    On the 2008 40FB I had that was Adelento built the bilge pump and fishbox pumps used their own dedicated hoses and all had valves at the transom where they exited the boat. Perhaps as your static trim changes water is migrating and that is what you see. I kept my bilge dry by using a Rigid Shop vac every so often. Fwd bilge always bone dry. Both engine room bilges and stern bilge I could get a small amount of water from after several trips. Pumps would never come on as I never would accumulate enough to warrant them cycling. I would manually check them occasionally. Not a big fan of those blue floats so will be changing mine to Rule Super switches soon.