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Old 15-07-2010, 21:56   #16
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What if the engine water discharge beats the rate of inflow. Then you have a seized engine as well as a big hole in the bottom!
Make the hole bigger

Dan
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Old 16-07-2010, 00:47   #17
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My Yanmar 3GM30F doesn't look like it puts out much water so I held a bucket under the exhaust. It runs about 2 gallons/min at 800 rpm. If it's linear with rpm that's 9 gallons/min at 3600 rpm. The Jabsco diaphragm pump, which was the only non-manual pump on the boat is rated at 6 gallons/min. The Jabsco actually puts out more like 3 gallons/min. In any case neither of these pumps are going to overcome any sort of a leak. I see no point in plumbing the engine intake as a bilge pump at this rate. I have added a 2000 GPH centrifugal pump, and am trying to decide whether I want to clutch a high capacity impeller pump on the engine or go a different route.

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Old 16-07-2010, 05:58   #18
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Centrifugal pump limitations

Will have a centrifugal pump on the shaft myself - thinking this would be the veritable "safety pump" but I guess if the shaft falls off the engine it is very limited to say the least! I think a clutched engine-driven pump is the go for controllable high volume pumping rather than the engine cooling pump - some expense but not as much as your boat and very simple to install and control.
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Old 16-07-2010, 06:01   #19
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This a a very real possibility. I have had two friends lose their boats by hull-fitting or connection failure. First they knew was stepping into knee-deep water in the cabin. Too late to identify incoming location and close apparently, difficulties getting the motor going, everything happening too fast and too confused. Maybe panic too. Anyway both went down in deep ocean. People OK.
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Old 16-07-2010, 06:56   #20
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I have always thought this a poor idea. When foundering presumably you are still making way towards safety and a moving boat will (I assume) be overcome by water more slowly and will roll later than a stationary boat. If you pick up some crud from the bilge you may compromise our motor and hence your charging and your radio and pumps.

So my thought has been to keep the motor running as best you can to buy time and distance to help.

There may be special circumstances where I would make a different decision.
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Old 16-07-2010, 07:32   #21
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I've always liked the signature "Rebel Heart" uses 'Keep the water on the outside, you on the inside, and the stick in the air' I like a water tight boat where the bilge pump switching on is an event worth taking notice of. Even on a boat that is a bit leaky, a second pump higher than the first can easily be rigged to sound an alarm. I'm always surprised by boats sinking when the first indication was water in the salon. The idea of using the engine cooling pump, to my mind is sensible as a low cost addition to your arsenal of keeping the water outside. If you are concerned about clogging the engine water intake, then a strainer can be fitted, or better still, keep your bilge clean and free of debris.

P.
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Old 16-07-2010, 11:47   #22
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The thing to remember about bilge pumps is that their exit holes need to be at least as big as the hole (or crack) in the hull letting the water in - and the deeper the hole the more pressure the water coming in is under the faster it arrives.

even with a couple of bilge pumps that doesn't allow for a very big hole below the waterline.........

Of course my maths could be wrong
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Old 16-07-2010, 12:01   #23
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I've always liked the signature "Rebel Heart" uses 'Keep the water on the outside, you on the inside, and the stick in the air' I like a water tight boat where the bilge pump switching on is an event worth taking notice of. Even on a boat that is a bit leaky, a second pump higher than the first can easily be rigged to sound an alarm. I'm always surprised by boats sinking when the first indication was water in the salon. The idea of using the engine cooling pump, to my mind is sensible as a low cost addition to your arsenal of keeping the water outside. If you are concerned about clogging the engine water intake, then a strainer can be fitted, or better still, keep your bilge clean and free of debris.

P.
I got it from my dad, who always tried to boil things down to what was really important. His other favorite: "Get that lee rail in the water!"
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Old 17-07-2010, 18:20   #24
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Be aware most of the well known brand submersible pumps output ratings are recorded at zero head, their output drops dramatically when resistance is applied.
The record of a scared man with a bucket has yet to be brocken.
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Old 17-07-2010, 18:33   #25
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Reminds me, of a recent radio conversation

"I have hit a rock and taking water"
Me " can you see the hole"

"Yes"
Me "Can you jam a cushion over the hole"

"The cushion will get wet!"
Me "I suggest a wet cushion is easily fixed"

What should I do"
Me "Head for a sandy beach and beach the boat, the tide is going out so you will heve time to sort out what to do!"
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Old 17-07-2010, 19:32   #26
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Make the hole bigger

Dan

LOL

Post of the week!!!

The geminis come with that standard. I added a hose that just sits there and is used when returning for a fresh water flush.

Of course the Gems don't have shafts and all like that ya know.
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Old 17-07-2010, 19:36   #27
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Reminds me, of a recent radio conversation



"The cushion will get wet!"



You are kidding right?
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Old 17-07-2010, 19:39   #28
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Now where is that thread where the math was done on a 2" hole a foot under (or so) and most all pumps anyone had would be worthless.

My 30B Three sucks about 2 gal in less than a minute at idle. No I have not actually timed it - crap, another project to do "just to know".
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Old 17-07-2010, 22:24   #29
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Now where is that thread where the math was done on a 2" hole a foot under (or so) and most all pumps anyone had would be worthless.

My 30B Three sucks about 2 gal in less than a minute at idle. No I have not actually timed it - crap, another project to do "just to know".

Another Bilge Pump Thread
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Old 17-07-2010, 22:42   #30
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Now where is that thread where the math was done on a 2" hole a foot under (or so) and most all pumps anyone had would be worthless.

My 30B Three sucks about 2 gal in less than a minute at idle. No I have not actually timed it - crap, another project to do "just to know".
No math, just go get a 5 gallon bucket put a 2" hole in it and push it under the water in a pool. Time it to the two gallon mark.

At a foot down one would think you could just heel it over and bring the hole out of the water.

Dan
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