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Old 06-04-2013, 13:39   #16
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Re: What do you all think of engine-driven bilge pumps?

Just a few facts for the discussion . . . .

I just looked up the pump rate of my yanmar cooling water pump. Running the engine flat out (3600rpm), with the thermostat pegged open (which it normally will not be), its very max flow rate is 3250l/hr, or 858g/hr, or 14g/min.

A 2" hole, 2' below the waterline will flood 113g/min.
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Old 06-04-2013, 13:45   #17
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Re: What do you all think of engine-driven bilge pumps?

Your looking at the cooling pump not the water pump">raw water pump. Raw water pump should not be through a thermostat. Even so They wont usually pump huge capacity but I can tell you it is better then the hand pump.
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Old 06-04-2013, 13:51   #18
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Re: What do you all think of engine-driven bilge pumps?

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Your looking at the cooling pump not the raw water pump. Raw water pump should not be through a thermostat. Even so They wont usually pump huge capacity but I can tell you it is better then the hand pump.
No, that is in fact the rated capacity of the raw water pump. It is RPM dependent (and 14g/min is the rate at 3600 rpm), but you are totally right and I was wrong to say it was also thermostat dependent (it's not).

Just looking at rule dc bilge pumps. The biggest one on their website, has a rate at a 6.7' head (and you need something like that sort of heat to prevent a reverse syphon) of 2157g/h at 12vts. or 36g/min. And that's a bigger pump that most people have in their bilge - 20amp draw.

Remember 2" hole 2' down = 113g/min flood rate.
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Old 06-04-2013, 14:20   #19
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Re: What do you all think of engine-driven bilge pumps?

A good hand pump is maybe 12 gpm Thats working and your not doing that long unless you scared shitless. maybe you get 14 gpm on a raw water pump but probably less. I was advocating for a tee as a last ditch back up. Also makes winterizing easy. it adds a option with little expense. A 2" hole is a big hole. Bilge pumps alone are not handling that for long.
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Old 06-04-2013, 14:49   #20
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Re: What do you all think of engine-driven bilge pumps?

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Originally Posted by estarzinger View Post
Just a few facts for the discussion . . . .

I just looked up the pump rate of my yanmar cooling water pump. Running the engine flat out (3600rpm), with the thermostat pegged open (which it normally will not be), its very max flow rate is 3250l/hr, or 858g/hr, or 14g/min.

A 2" hole, 2' below the waterline will flood 113g/min.
and remember your big boat has a big engine with a big raw water pump and that hole fills your big boat slower. The same hole in my smaller boat lets in water at the same rate, there is less volume to flood ( I sink faster) and my smaller raw water pump is even more feeble by comparison.

An experienced salvor explained to me that the job of the bilge pump is to give you as much time as possible to find and fix the hole. Forget about actually making headway against the flood until it is stopped. My time can be better spent than fooling around in the depths of the engine compartment trying to switch the valve, which is now underwater of course.

Find and fix the leak quick or start getting your ditch bag.
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Old 06-04-2013, 14:58   #21
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Just finished reading a story of a couple in the Med. Long story short, they suffered a knock down while at anchor. Had water flood down companionway and lost the ability to start the engine. They did have an OMG size bilge pump as thief last line of defense. That pump kicked in and got enough water out that when the next knock down came (caused by collision with another boat that as pulling anchor) they were fine.

From what i have read, the huge electrical pump wired to the batteries is bulletproof. If you have engine, it will power the batteries indefinitely. If you loose the engine you still have the pump for as long as the batteries last.

Bill

PS If I find where I read story I'll post the reference.
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Old 06-04-2013, 15:00   #22
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Re: What do you all think of engine-driven bilge pumps?

I can lift water from the bilge via an engine driven pump with a clutch. It has a larger diameter (1") hose than my cooling water pump. I won't use it unless my other pumps get clogged.

If the engine isn't running the engine driven bilge pump is useless.

Electric pumps only last as long as you have battery power.

Manual pumps give out only when you do. I'll always have a manual backup and some buckets standing by.

kind regards,
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Old 06-04-2013, 15:02   #23
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Re: What do you all think of engine-driven bilge pumps?

Most of the common impeller pumps dont move much water. For the $ and complication I'd go another way personally.
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Old 06-04-2013, 15:40   #24
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Re: What do you all think of engine-driven bilge pumps?

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Originally Posted by estarzinger View Post
...
A combination of the above two . . . AC pump plus say a Honda 2000 gen is a workable hybrid solution. The Honda will get used in its normal gen/battery charging role, so will be used and maintained and actually run if needed in an emergency.
....
I like the idea of a genset plus AC trash pump. Not sure a decent sized one would actually work with a Honda 2000. The running current of a Honda electric 110GPM pump (1/2 HP) is 8.3amps, but the startup current is 34amps. Not sure a Honda 2000 can deliver this at startup.
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Old 06-04-2013, 15:50   #25
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Re: What do you all think of engine-driven bilge pumps?

There's a Rule 3800 GPH 120v bilge pump. IF you already have the Honda that would work. If not there are gas powered very small Honda trash pumps for about $600 and up that are pretty slick. about the size of a gallon of milk!
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Old 06-04-2013, 18:24   #26
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Re: What do you all think of engine-driven bilge pumps?

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gas powered very small Honda trash pumps for about $600 and up that are pretty slick. about the size of a gallon of milk!
Do you have a link to the specs on the "gallon sized" gas pump? I have never seen one that small.
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Old 06-04-2013, 18:31   #27
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Re: What do you all think of engine-driven bilge pumps?

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Do you have a link to the specs on the "gallon sized" gas pump? I have never seen one that small.
I was curious myself, and found these:

Honda WX10

This one pumps at 37 GPM (at what head???), and weighs 13.4 lbs.

They have a larger one:

Honda WX15
72 GPM, 20 lbs, $530 MSRP.

These aren't nearly as powerful as a real trash pump, but way better than most bilge pumps. I wish they spec'd flow rate vs head.
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Old 06-04-2013, 18:33   #28
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Re: What do you all think of engine-driven bilge pumps?

try this
.Earth Quake Portable 1in Water Pump w Gas Engine
Problem is gas and will the thing start.
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Old 06-04-2013, 18:40   #29
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Re: What do you all think of engine-driven bilge pumps?

Someone observed that the Bounty was not well served by an engine-driven bilge pump.

I don't think this is correct.

My understanding is that the only high capacity pump on Bounty was a mains electric (ie AC) pump, which relied on a genset. The gensets in turn would almost certainly have relied on the DC electrical supply. This would have quickly become unavailable due to flooding, a classic Catch-22.

It seems to me axiomatic that a traditional planked ship or sailboat should have two essential elements:

A large diesel motor which can be started (by hydraulic or spring starter) and run, BOTH without any electrical supply, and with a completely flooded engine room.*


It makes sense for this engine to be the main propulsion engine, partly because it needs to be similarly independent of other services in emergencies, and partly because it will be better maintained than any other engine.

This engine should be coupled to at least one direct driven pump which can pump sizable debris without turning a hair, and this pump or pumps should be sized to monopolize the output of that engine, if the output falls in the category of 'auxiliary' power. (It seems that the Bounty pump was woefully undersized, as well as insufficient in number, and inadequate in terms of availability)

Naturally there can and should be other pumps, but they should be viewed as a convenience and a supplement: their availability should in no way be relied on.

*This engine should have a second, emergency fuel supply sufficient for six hours running, gravity fed, preferably a sealed tank with an internal bladder in lieu of a breather (but beware of fuel heating issues from injector bypass) and easily refillable by hand pump.

If it's not the main propulsion engine, it should be capable of jump-starting the main engine, perhaps by a dog-clutch on the donkey engine, a one-way clutch on the main engine, and a suitable belt drive. Preferably the main engine will have decompressors, in this scenario.

It seems to me that it's lessons like this which should be learned from what happened to the Bounty, but these days it seems fashionable to look elsewhere than the basic, unglamorous, "chips down" grease monkey technologies, even when there is more than enough blame to go around.
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Old 06-04-2013, 18:42   #30
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Re: What do you all think of engine-driven bilge pumps?

^^
Thanks, interesting.

Re flow rate with 'typical head', I usually figure half the zero head output.

Just for example . . . for one of the rule pumps, its 30GPM at zero head (which is the marketing flow rate), 21GPM for 5' of head, and 12GPM for 10' of head. And I figure the best practice anti-syphon installation has 6" or so of head.
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