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Joe
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Joined: 5/19/20
Posts: 9
Using engine as emergency bilge pump?

So I did a stupid (and expensive) thing today and accidentally drilled a hole in the hull below the waterline in my 1983 MK I.  Luckily the bilge pump kept the water at a reasonable level for the short time I needed to get the boat hauled out.  It was almost certainly a losing battle, but the water didn't rise above the bilge and I had the shower sump pump turned on as a backup in case the water got to that level.  This ordeal got me thinking about the other pumps on the boat that might be useful in emergency situations if the bilge pump failed for whatever reason or could not keep up.

I'm considering splicing in a T junction and additional ball valve between the engine water intake seacock and the engine water filter.  I'd run a hose from that ball valve into the bilge.  In emergency situations, I could shut the seacock and open that valve to use the engine as an additonal pump.

I'm very interested in hearing others' thoughts on this.  Is this a bad idea?

Joe T. Sylve, Ph.D.

S/V Stargazer
New Orleans, LA

1983 Catalina MK I
Hull #0076

Paul Revere
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Joined: 3/30/19
Posts: 30

I've seen this done on some youtube sailing channels. Ive been thinking about it myself honestly.
My only concern is the water pump not being able to suck the water up fast enough to cool the engine. I recently had some seaweed just slowing the flow through hull and the Temp climbed right up with the reduction in pressure.
It would only make things worse to overheat the engine trying to use it as a bilgepump in addition to the reason your taking on water in the first place.

A better solution is to get a 120v sump pump that you can leave in the Bilge, and run it off your inverter/batteries as your alternator charges. It will move far more water than your engine or a 12v can.
I recently saw a test, it emptied a 20L container in I think around 30 seconds, the improvised engine bilge did it in 2:10 and a hand pump did it in 1:55.

Joe
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Joined: 5/19/20
Posts: 9

Thanks for the response.  Pretty much everything in my boat except for the airconditioner is DC, so I don't have an inverter on board.  I think it might be worth picking up a cheap one with just enough power for a high flow pump for this purpose.  I suppose it would also be useful for charging cellphones, etc.  With all the crap that inevidably makes it way into the bilge, I had too considered that it might not be a good source of water to cool the engine.  Seeing water coming into your boat just makes your mind go to weird places, I guess.

Paul Revere
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Joined: 3/30/19
Posts: 30

Just make sure the inverter can handle the starting load of your pump. Your batterys and alternator also need to be up to snuff to maintain that kind of load, a single 12v house and a stock 50A on a V belt aren't going to cut it. Just looking up a good sump pump at home depot, the running load is over 1000w, so you'll probably need a 2000w inverter to handle the starting load.

I didn't consider the debris getting sucked up, Though that seems like it could be solved with a wire mesh cap over the end and cleaning out the heat exchanger once your on the hard. I was more thinking the pump having to create the suction by itself rather than being assisted by the pressure. You would also have to prime the hose you have going to your bilge to use it, probably by leaving the thru hull open for a few seconds after you opened the bilge feed till water came out of the bilge hose. If you had your engine in neutral I think it would be fine as far as overheating, though that defeats the purpose of trying to stay afloat to get to a haul out.

Easiest solution and most effective solution is the old one, to get wet and hammer in a plug or have some good goop that will set in water that you can slather on a crack so the leak stops to nothing more than a dribble and your regular 12v bilge's can keep up no problem.

At 2ft below the waterline, a 2 inch hole is letting in 111 gallons a minute. That's about all the 1hp pump your gonna squeeze in there will handle. Anykind of leak bigger than that, and your on borrowed time to slow the flow or get hauled out.

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Ray Taylor
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Joined: 9/11/19
Posts: 27

We have this arrangement on our boat.  A short section T from the main line with a 90 deg ball valve.  It was installed by the former owner to routinely flush the engine and exchanger passages.   We use it primarily for winterization.    That said it would be my last resort to use as a bilge pump.  

I like to keep it simple and reliable:   

  • A robust DC powered bilge pump and reliable float switch. 
  • A manual bilge pump near the helm
  • 2 gallon bucket
  • Dedicated leak repair crash kit

    Keeping water on the outside is important. 

Zefyros
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Joined: 5/8/15
Posts: 11

Back up on back up. 

Different  power sources. Different exhaust ports.  2 more bilge pumps forward, but they drain into the main bilge. 

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Joe
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Joined: 5/19/20
Posts: 9

Wow!  Your bilge is beautifully clean.  What's your routine for that?

Zefyros
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Joined: 5/8/15
Posts: 11

Thank you.
3 drips per minute :) 
I stopped all leaks. The top of the mast is sealed as well as possible.The mast hull entrance is tighter than the keel itself. If there there is condesation in the bilge, I vaccum it out. I wipe any residue and repaint every few years. My OCD is not hurting the situation either :)

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KevinLenard
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Joined: 1/28/15
Posts: 158

Well now you have me intrigued. Using this as an intellectual exercise and engineering challenge, I would think that there's a risk and having a tee off of the raw water pump intake, only in so far as if you leave the through hole open and open the valve off of the Tee, you now have the risk of water flowing directly into your bilge. This could be solved with an anti siphon loop, or always being sure to close the through-hull first, but it could also be solved by having a 2-way splitter at the Tee, instead of just a valve after the Tee. If there was a Y-valve, you could choose to have some water start to come in from the outside as you start the engine and then switch off the exterior Source entirely. This set up might require two people on board, especially in a crisis situation, but some jumping up and down might accomplish it. Also installing a one way backflow preventer on the extension hose into the bilge would remove some of the risk.

I have one of those red foam emergency plugs on board, but the reality is that most serious hull damages are going to be cracks, not round holes. I also have some of the miracle underwater-setting putty that I foolishly have not put in the same easy access spot as the red plug. I'll move it now!

The reality is that in a crisis, likely in the dark with heavy waves and wind, you are not going to be in a position to get down on your hands and knees and dive under the incoming water to fill the crack. Your best bet in those circumstances would be to have an emergency backup bilge pump running off a separate power source such as the engine, but once the batteries are submerged you may find yourself calling a Mayday and looking up your insurance policy number...

pierview
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Joined: 9/27/09
Posts: 501

Using the engine with this arrangement is very common on boats owned by those "others" (ie... sport fisherman boat owners).

cmhuber
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Joined: 2/15/14
Posts: 16

You could use a 12 volt sump pump like the pumps people have hooked up to batteries as back up home sump pumps. I suppose you could attached a set of battery cable clamps to to the pump for a quick connection to your house battery bank. You could run the discharge hose up to the cockpit.

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