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Old 10-18-2017, 05:41 PM   #1
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How Do You Determine What Size Bilge Pump You Need

How do you know what GPH pump you need?
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Old 10-18-2017, 06:04 PM   #2
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Simple for me, the biggest you can afford that will fit in the space.
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Old 10-18-2017, 06:16 PM   #3
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There is no right answer beyond one bigger than your biggest leak...whatever and whenever it is.

It is a complex risk management decision that only the boat owner can rubber stamp.

There are rules of thumb that I find a folly, yet you can feel satisfied by being reasonable then multiplting by 3.
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Old 10-18-2017, 06:17 PM   #4
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Like mentioned biggest but it should at least be able to pump the biggest water intake volume you can face in case of something breaks like a raw water hose. Of course this does not apply to major structural damage as I don't think any pump will support a 4 square feet hole

I inadvertently tested earlier this year that my 2000gal/h is correctly sized

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Old 10-18-2017, 06:48 PM   #5
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I always have thought this article has some good basic info, a bit dated but still quite relevant as to the issues. :

ALL ABOUT BILGE PUMPS - Boats, Yachts Maintenance and Troubleshooting
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Old 10-19-2017, 07:03 AM   #6
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Quote:
Originally Posted by kartracer View Post
How do you know what GPH pump you need?
Don't feel bad about adding a second bilge pump if you wish.
I added a second bilge pump on my Nordhavn and set the discharge to the opposite side of the first pump.

At least one bilge pump in each bilge area. Some compartments are not totally water tight.
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Old 10-19-2017, 07:11 AM   #7
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"There is no right answer beyond one bigger than your biggest leak...whatever and whenever it is."


That is what I thought also !!!!
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Old 10-19-2017, 07:24 AM   #8
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Also consider that the installed capacity is seldom what is advertised. There are several quick switches for raw water intake from bilge that can add emergency capacity and might be worth considering based on cruising style.
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Old 10-19-2017, 08:03 AM   #9
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Let's face it, you get a high water alarm, you will go find out why. If it's a hose, you will shut the hull valve.
If you holded the hull, you have more important things to do, launching the dingy and or survival raft, gathering up the UHF radios and food and water.
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Old 10-19-2017, 08:08 AM   #10
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Do more boats flood/sink at the dock than while underway?
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Old 10-19-2017, 08:10 AM   #11
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Quote:
Originally Posted by Lou_tribal View Post
I inadvertently tested earlier this year that my 2000gal/h is correctly sized

L
Sooo, tell us about the 'inadvertently"????

Yup, centrifugal bilge pumps are pretty good at sucking but the discharging can be a problem.... That is why I had suggested, if you put in a second bilge pump, discharge it to the opposite side. Seldom do boats sink 'flat' when underway.
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Old 10-19-2017, 08:20 AM   #12
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Simple for me, the biggest you can afford that will fit in the space.
And for us, two more further up with float switches at different heights
And two more of same in the spares locker
And two submersible 240v ones that can be moved around as required
And a spout and valve off the raw water in before the strainer that can be used to suck bilge as main engine runs.
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Old 10-19-2017, 08:22 AM   #13
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I have a spare bilge pump with a long discharge hose and powered by long 12vt battery clamps.
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Old 10-19-2017, 08:27 AM   #14
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Quote:
Originally Posted by OldDan1943 View Post
Sooo, tell us about the 'inadvertently"????



Yup, centrifugal bilge pumps are pretty good at sucking but the discharging can be a problem.... That is why I had suggested, if you put in a second bilge pump, discharge it to the opposite side. Seldom do boats sink 'flat' when underway.


Well last spring when we departed from our dock for a 1 month trip we had a "little incident", the main raw water hose connected to the exhaust manifold popped out and the engine was pumping water in the ER directly.
To make it short first thing I did when I notice the 2 feet of water in the ER is to force the main pump on and turn back to the dock. The pump was strong enough to keep up with the flow of water coming in while we were underway. ( before any comment yes I could have reconnected the hose and solve the issue but under the stress of the situation I did not notice the disconnected hose and was just thinking not to sink in the middle of the river )

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Old 10-19-2017, 08:32 AM   #15
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To make it short first thing I did when I notice the 2 feet of water in the ER is to force the main pump on and turn back to the dock. The pump was strong enough to keep up with the flow of water coming in while we were underway.

L
2 feet of water? You ER must be bigger than mine. 2ft of water in my ER would be catastrophic. It would overtop the bilge pump.
What diameter a hose was it?

2 ft? Time to set the float switch and high water alarm lower in the bilge.
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Old 10-19-2017, 08:36 AM   #16
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How Do You Determine What Size Bilge Pump You Need

Quote:
Originally Posted by OldDan1943 View Post
2 feet of water? You ER must be bigger than mine. 2ft of water in my ER would be catastrophic. It would overtop the bilge pump.

What diameter a hose was it?


I think the hose size is 2 inches and yes the pump was submerged water was half way the engine and I took it at the right moment few inches more and it would have reached the air filter
Good thing is that it cleaned my engine bottom and ER lol Better laugh about it now!
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Old 10-19-2017, 08:43 AM   #17
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Good thing is that it cleaned my engine bottom and ER lol Better laugh about it now!
L
And lots of fresh water used to hose out the salt too.
That is one way to clean the bilge but, I would not recommend it.
Glad you were able to recover.
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Old 10-19-2017, 08:54 AM   #18
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Quote:
Originally Posted by Lou_tribal View Post
I think the hose size is 2 inches and yes the pump was submerged water was half way the engine and I took it at the right moment few inches more and it would have reached the air filter
Good thing is that it cleaned my engine bottom and ER lol Better laugh about it now!
L
Scary and no fun at all.

But you had what I knew in the USCG as a self correcting sinking.

When the engine quits, the inflow of water most of the time stops too.

Respnded to several vessels where just that happened.

Not a good way to save the boat....
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Old 10-19-2017, 09:15 AM   #19
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Any way one can recover from a sinking is a good way. It may not be "pretty" but if it works who cares.
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Old 10-19-2017, 09:20 AM   #20
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Bigger is better. On my 32' boat I have three electric bilge pumps. On either side of the keel I have a 2,000 gph pump and I have a 4,000 gph pump on top of the keel. Each pump has its own float switch. The switch for the 4,000 gph pump is located above those for the 2,000 gph pumps. So far the 4,000 gph pump has never run (except in tests). Another consideration is the electric draw of your pumps and how that relates to your battery capacity. My 2,000 gph pumps draw 7 amps and the 4,000 draws 20 amps. Needless to say, the 4,000 gph pump would flat my batteries if it was running and the boat was unattended for 24 hours. Fortunately at the end of the season my smaller pumps were only running for 8 seconds a day so I was drawing a trivial amount from my batteries which my solar replaced within minutes.
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