Aft bilge pump lets water in?!

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

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.




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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.

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.

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.

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!

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!