Another approach for an emergency bilge pump.

Looking at the Rule 4000 gph bilge pumps which seem to be up there amongst the best, one still wonders how much water they can remove with say a 7 foot lift. Then I started looking at these babies, their prices are sure in the reasonable zone, BUT BUT BUT - - they can remove 5,600 gallons/hour with a 10 foot lift.

Now that's what I call dewatering.

 

The Rule 4000 gph bilge pump has about 2,400 GPH at 3' lift, which translates to 40 gallons a minute. The 2" gas model you've linked will do about 115 gallons a minute, at 3' of lift, which is a substantial difference. Gas pumps always out preform the little 12 VDC versions, but typically aren't self starting and they're heavy, need fuel and a much higher maintenance routine. Gas units often need to be primed and can suck air and shut off too. Because of inlet sizes, they can swallow bigger chunks of debris before they choke, compared to small 12 VDC units.

The 12 VDC pumps have a much smaller foot print, don't need exhaust routing, can be placed about anywhere and can be a set and forget arrangement.

I have a 3" Honda that I use to save and recover boats with and it does kick butt. It weighs a hundred times what a big 12 VDC unit might and isn't automatic starting. If your boat is tight, then the 12 VDC units are fine, but if you think you might need a real kick *** pump, then go pick up a gas unit and keep it in good shape.

 

At $279 and if you have plenty of spare space in deck boxes like I do with the outboard and its tank - it's remarkably cheap insurance to keep one of these babies well maintained and available for emergency dewatering! Worth plumbing in a coarsely screened pipe in the deepest part of the bilge...

 

Gasoline is dangerous, doesnt like to get wet and once you get pumping you will certainly run out of gasoline.

All commercially registered boats Ive sailed had diesel powered emergency fire, bilge pumps.

http://www.dawest.com/pumps.html

Check your flag state rules concerning installation of emergency pumping. To increase flow rate Many pumps are deployed without the anti siphon loop and vented directly via a seacock.

 

These are the typical pumps you use to dewater building sites, pump out dams.

Move a lot of water fast. Inlet is high and these centrifugal pumps like gravity fed inlets otherwise you get cavitation due to airpockets.

A diesel double acting diaphram pump would be my choice. You can angle the inlet down into the bottom of the bildge to get the water down to a lower level.

Diaphram pumps do not "silt up" as do centrificals.

They will not pump as fast, but don't mind pumping with no water as there is no rotating parts to overheat in the pump. A diesel can be self started if required.

Don't forget any aircooled engine is not designed for below deck work.

Poida

 

When you've already got a gasoline outboard tank on deck for the outboard, to get 2 or 4 hours of serious dewatering to get at the problem makes the "danger" of petrol pretty irrelevant, and the almost disposable worth-it-if-you-use-it-once $279 bucks is pretty hard to beat.

If you can afford it (and I would if I can, you can find a reasonably priced diesel unit for nearly three times the price, but it's getting to the point where it's prohibitive, also bigger and heavier. http://usatoolsinc.com/3dieselwaterpumppoweredby4-strokedirectinjectionenginegdp30cle.aspx

 

Ray,

Rule publishes data on head and voltage variables that will answer your questions and provide food for thought regarding your application and what you may (or may not) need.

-Tom

P.S. Don't forget your engine's salt-water pump as an alternative/additional emergency bilge pump...

 

And dont forget dedicated emergency pump suction and discharge plumping. Never share the fixed bilge pumping plumbing.

The electric Rule pumps are very good emergency pumps. Cheap and they move plenty of water. Install them high in the bilge inside a 5 gallon bucket sized sea strainer with float switch and alarm . Installed high means that the installation never gets wet until you need it.

The defect of engine driven bilge pumps is that the reason you are sinking is a plumbing failure in the engine room. Normally you shut all sea cocks...including the main engine cooling , as you investigate.

The last major leak incident I had was a ruptured flexible main engine exhaust hose . The engine was useless for pumping.

 

I also see some use in these pumps as fire fighting equipment.

 

As an engine driven pump, the twin chambered Stiemel type KB centrifugal is widely used on yachts. This pump cools the engine with one chamber while its second chamber continuously scavenges the bilge.