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Old 13-07-2016, 10:38   #31
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Re: Bilge Pumps Versus Holes In The Hull

So another technique I heard was to break the inlet hose to the raw water cooling, turn off the sea cock of course, and let the engine pump-out the water.
The only time I needed a bilge pump of course was when this happened in reverse and the engine tried to fill the boat with water whilst overheating. Ho hum.
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Old 13-07-2016, 10:45   #32
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Re: Bilge Pumps Versus Holes In The Hull

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Originally Posted by davewtsnape View Post
So another technique I heard was to break the inlet hose to the raw water cooling, turn off the sea cock of course, and let the engine pump-out the water.
The only time I needed a bilge pump of course was when this happened in reverse and the engine tried to fill the boat with water whilst overheating. Ho hum.
Hard to imagine my little Oberdorfer raw water pump being very tolerant of crap floating around in the bilge water...
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Old 13-07-2016, 11:02   #33
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Re: Bilge Pumps Versus Holes In The Hull

This is an area where light, foam sandwhich multihulls come into their own. There is no hurry to pump them and they can never be awash within nor sink.
I have owned such boats and crossed many oceans in them and can attest to this. The first one I built, a GBE, I simply pulled a plug in the sump and let any accumulated rain drain out, no pumps at all.
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Old 13-07-2016, 11:03   #34
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Re: Bilge Pumps Versus Holes In The Hull

+1 for Stay Afloat.

I retired my wood plugs for several tubs of Stay Afloat because leaks don't always come in the form of perfect round holes nor is there always room to swing a hammer.

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Old 13-07-2016, 15:09   #35
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Re: Bilge Pumps Versus Holes In The Hull

"Originally Posted by davewtsnape View Post

So another technique I heard was to break the inlet hose to the raw water cooling, turn off the sea cock of course, and let the engine pump-out the water.
The only time I needed a bilge pump of course was when this happened in reverse and the engine tried to fill the boat with water whilst overheating. Ho hum."

"Hard to imagine my little Oberdorfer raw water pump being very tolerant of crap floating around in the bilge water... "

My boat is actually rigged to use the engine cooling pump as a bilge pump in an emergency. I just have to open one valve and close the seacock. The bilge water goes through the strainer before it reaches the engine so it is unlikely that the engine would be damaged by debris.

My engine has an 1-1/4" pump so it moves some water. The little 3/4" pumps common on sail boat engines might not be as much help.
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Old 13-07-2016, 16:55   #36
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Re: Bilge Pumps Versus Holes In The Hull

While you can gain a considerable advantage from a bigger pump with a bigger diameter hose, and a bigger diameter discharge mushroom, you gain nothing in lift from those improvements. It appears that all these centrifugal pumps produce about 6 PSI, and any old fireman can tell you that you lose 5 PSI per "floor," actually 12 1/2 feet. That's simple hydraulics independent of friction loss, hose size, and the like. Go up four feet from pump to discharge, and the 1 1/2 to 2 PSI you have lost is a third of the maximum flow you'll get out of that pump.
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Old 13-07-2016, 17:06   #37
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Re: Bilge Pumps Versus Holes In The Hull

Thru hulls with a ball valve are not a great idea compared to a flanged sea cock bolted, screwed or glued to the hull.

Unless you have no clue, a true thru hull should never allow you to sink. That's why they exist, and a lever to shut off the flow of water for the things that might fail more often.

Two, bilge pumps will never really keep up with a hull breach, unless you have several gas powered trash pumps. Bilge pumps hopefully keep up with minor issues when away from the boat, but otherwise, they are designed to remove the leakage thst gets past your damage control...no good damage control and sinking might be a probability.
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Old 13-07-2016, 18:33   #38
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Re: Bilge Pumps Versus Holes In The Hull

The old "raw water cooling pump as bilge pump" legend. My Westerbeke W30 exhaust, running full out, does not look like it puts much more water out than my small Whale Supersub 600.
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Old 13-07-2016, 18:54   #39
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Re: Bilge Pumps Versus Holes In The Hull

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Someone awhile back questioned my concern that a popped seacock could sink a boat despite the presense of bilge pump(s), so I decided to dust off my 50 years ago fluid dynamics course notes and also scrounge around the internet on the issue. I actually found one formula on the internet that has gallons per minute and per second confused.

The starting point model I'll use is a 1" popped seacock located 3 feet below the waterline. That computes out to 34 gallons per minute. That calculation is easy and pretty robust; it's the lift by the pumps and particularly the friction loss in the hose and fittings that gets hazy.

Pumps are rated with no intake obstructions and no hose attached, so 1600 GPH = 27 GPM, 2000 GPH = 33 GPM and 4000 GPH = 67 GPM (Johnson 4000, the largest I could find on the ready market). Even at rated capacity, only the 2000 GPH and up are going to keep up with our 1" hole.
When BoatUS looked at them, they could not find one that did better than 75% of its rating at 12.0 volts. Let's assume 13.4 volts and give them full rated output. But, these little centrifugal pumps only put out about 6 PSI, so you don't have much to work with either for pure lift (goes to zero PSI at about 14 feet of lift) or friction loss (varies with hose diameter, smoothness, bends, and length).

At an assumed 4 foot lift, through 10 feet of smooth hose and no sharp bends, the answer is about 60% of the rated capacity for the smaller pumps. Part of that is head , which costs you about 2 PSI, and part is friction loss in 3/4" hose. Standard friction loss tables for lined fire hose say that at 30 GPM the friction loss is 10.5 PSI per 10 feet, so you see where we're going - the larger the pump, the greater the friction loss percentage. Even a very big pump won't put 30 GPM through a 3/4" hose 10 feet long. 1" hose helps immensely, dropping friction loss at 30 GPM to 2.6 PSI for 10 feet.

Then put the stream through a necessarily constricting thru-hull (think of it as a nozzle), and you get less than 40% of rated output. These are not fire pumps. A different assumed model used by BoatUS and actually tested discharged 26% of its rated capacity.

Let's call it an optimistic 50% and move on. That gets you 13, 16, and 33 GPM. Only the Johnson might keep up with our 1" hole, and it better have 1" hose, but the others may slow things down enough to give us time to get to the seacock. The 1600 optimistically slows it to 20 GPM into the hull.

That leads to a second but I think the central question for cruisers. How many gallons can enter your hull before the tops of your battery bank are reached? Once that happens we don't have electric pumps. Given a popped 1" seacock, how many seconds do you have to realize the problem and stop it? I know that for mine, the answer is "not very many" if the hole in in the forward cabin with the battery bank, but I only have two seacocks, and they're in the engine room. One stays closed (sewage) and the other can be closed by pulling a wire in the main salon above it. I do need to remember to keep the engine room door dogged shut, and to exercise my gasoline OMG pump frequently.

I'll have to agree with BoatUS on this issue - They say the priority must be stopping the leak, because the pumps we have are not likely to keep up, and pump only a fraction of their rated capacities.

Thoughts?

Sounds like everyone is afraid to get their toes wet. Just stop the boat, grab your mesh bag full of plugs, and swim mask , then clip on to a rope and jump over the side and stick a plug in the hole. At night use a flash light. What's the big deal? Everyone has been advised to have an assortment of plugs on board just for that reason , Who doesn't have a swim mask onboard? a one inch hole could be plugged with an old fashioned thermos bottle plug. Keep a few plugs on board that will fit every single though hull hole in the entire boat and you'll never need them. But if you don't carry any , then guaranteed you'll need one at the worst time.
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Old 13-07-2016, 18:56   #40
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Re: Bilge Pumps Versus Holes In The Hull

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Originally Posted by sanibel sailor View Post
The old "raw water cooling pump as bilge pump" legend. My Westerbeke W30 exhaust, running full out, does not look like it puts much more water out than my small Whale Supersub 600.
John, if you had a real engine instead of that tiny girly thing, it would move some real water. Did you paint your engine pink?

Seriously it might not be effective for most sailboats but boats with bigger engines can benefit from rigging the cooling pump to easily pump the bilge.

Both Groco and Perko make systems to do that and also make it easy to flush or winterize the engine.
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Old 13-07-2016, 19:39   #41
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Re: Bilge Pumps Versus Holes In The Hull

taper bungs are for through hull fitting failure/leaks can be all different shapes as with Jessica "Pink Lady" / if you collide with a container that is still connected to a large ship and survive without creating hull leaks and patch up the boat to sail around the world in the process run over a huge steel fishing mooring still without any hull leaks then have an emergency with water in the bilge from port lights leaking / a professional fishing boat made it into port bow down with the rudder and occasionally the prop breaking the surface due to lack of maintenance and timber planking opening up in the sun while on a swing mooring when the owner steamed into a heavy sea a surprising amount of water flooded the crew compartment but was held by the bulkhead / forward pump was slowly losing / the vessel got in before the prop and rudder were clear of the water .
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Old 13-07-2016, 19:50   #42
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Re: Bilge Pumps Versus Holes In The Hull

It's not like I don't have enough going on. Now I'm spending online time looking at engine mounted pumps with an electric clutch.
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Old 13-07-2016, 22:31   #43
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Re: Bilge Pumps Versus Holes In The Hull

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Originally Posted by Rorzech View Post
Sounds like everyone is afraid to get their toes wet. Just stop the boat, grab your mesh bag full of plugs, and swim mask , then clip on to a rope and jump over the side and stick a plug in the hole. At night use a flash light. What's the big deal?
Crocodiles, sharks, stinging jelly fish to name a few. But maybe I am just a wimp
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Old 14-07-2016, 03:44   #44
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Re: Bilge Pumps Versus Holes In The Hull

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Originally Posted by Rorzech
Sounds like everyone is afraid to get their toes wet. Just stop the boat, grab your mesh bag full of plugs, and swim mask , then clip on to a rope and jump over the side and stick a plug in the hole. At night use a flash light. What's the big deal?
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Crocodiles, sharks, stinging jelly fish to name a few. But maybe I am just a wimp
20 ft waves, 34 deg F water.

Climbing over the side is fine if you are in a bay on a clear, calm night in the tropics.

Seems that leaks (weak pipes, through hulls or drain plugs) sense that you already have enough issues to keep you busy. Then they open up just to see if you'll notice...
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Old 14-07-2016, 09:07   #45
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Re: Bilge Pumps Versus Holes In The Hull

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Originally Posted by sanibel sailor View Post
The old "raw water cooling pump as bilge pump" legend. My Westerbeke W30 exhaust, running full out, does not look like it puts much more water out than my small Whale Supersub 600.
Yeah, always thought it was a waste of time and money. Very little reward for that. You can buy a Honda gas pump that puts out a steady strong 1" stream pretty cheap if you want a power pump. I think they are $550-600
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