Auto bilge pump

ghostlymoron

ghostlymoron

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I've just read in another discussion that it's common to wire an auto bilge pump direct to the battery. I've had a boat wired like this but would it really save your boat if there was a catastrophic leak? A decent sized pump draws quite a bit of juice so would flatten the battery in no time.
It may work in a marina with a sharp eyed attendant but not on my mooring in an unattended lagoon. I'd just sink with a flat battery.
 
ghostlymoron said:
I've just read in another discussion that it's common to wire an auto bilge pump direct to the battery. I've had a boat wired like this but would it really save your boat if there was a catastrophic leak? A decent sized pump draws quite a bit of juice so would flatten the battery in no time.
It may work in a marina with a sharp eyed attendant but not on my mooring in an unattended lagoon. I'd just sink with a flat battery.
Click to expand...

No, it would simply delay the inevitable. Much better idea is to check that your seacocks, hoses, etc, are in good condition.
 
Doing this live after half a bottle of Sauvignon Blanc so forgive any errors ...... I've got 600 Ah of house battery which the solar panel keeps fully charged. Let's assume the sun sets at 4:00pm and after that it's not doing anything. Lets assume that the bilge pump is 10A, which would be a really big one, it would run for 60 hours continuously after sun-down and that would be shifting something like 30 gallons per minute which would be a huge leak.

Assuming something less catastrophic and therefore intermittent operation, the sun will come up next morning before too much has been drawn from the battery. Even if the sun doesn't appear next day, we could be talking about many days (or even weeks) of intermittent operation before the batteries final run out of steam.

Richard
 
ghostlymoron said:
I've just read in another discussion that it's common to wire an auto bilge pump direct to the battery. I've had a boat wired like this but would it really save your boat if there was a catastrophic leak? A decent sized pump draws quite a bit of juice so would flatten the battery in no time.
It may work in a marina with a sharp eyed attendant but not on my mooring in an unattended lagoon. I'd just sink with a flat battery.
Click to expand...

A auto bilge pump should be wired to a fuse and switch panel, so you can also tell it to go pump stuff in case the automatic switch has failed (or you want to get that last bit of soup out of the bilge) - or turn it off when it is running dry because the automatic switch has failed the other way. You'd normally leave it on auto.

bilge-pump-panel-switch.jpg
 
In practice once installed most bilge pumps actually pump considerably less than their quoted rate, and sometimes draw a bit more power than they say they use. I assisted in the work involved when a friend's elderly and not very well maintained large clinker wooden boat was left on a mooring relying on an auto pump and batteries. It sank....
 
jwilson said:
In practice once installed most bilge pumps actually pump considerably less than their quoted rate, and sometimes draw a bit more power than they say they use. I assisted in the work involved when a friend's elderly and not very well maintained large clinker wooden boat was left on a mooring relying on an auto pump and batteries. It sank....
Click to expand...

Sounds like Dad's old boat! He had a moderate battery bank and the boat was kept afloat on an auto pump. He would check it once a month or so, and had fitted a clock in the pump circuit to record how many hours the pump had run. The disadvantage was that if it went over twelve he would know if it was 6 or 18 hours....

I have occasionally left an auto pump continuously live, when off the boat, primarily for a troublesome rudder stock leak. The pump would run for a around 10 seconds each hour. Battery consumption was maybe 1 or 2 percent capacity a week. I consider that a serious leak that needs urgent attention is one that is requiring more than. 1% duty cycle on the pump, so something that is running a pump for 30-40 seconds an hour. Even that will not have a great effect on battery capacity.

A catastrophic leak that is going to exceed pump capacity is only likely to be from a collision, or a seacock/pipe failure. If all seacocks are closed on leaving, then an auto pump should do fine for any other leak. It should probably even keep up with a failed stern gland.
 
I know a lot of people who use auto bilge pumps successfully for moderately leaky wooden racing boats, and also for open boats like RIBs etc.

I don't think they have much role on a typical GRP yacht, where the most likely thing they will do is pump oily bilge water into a marina.
That's fine as in £1000 fine, do not pass go.
They won't cope with a big leak like a failed skin fitting.
If you have rain getting in and being pumped out regularly, your boat will be damp and manky.
Sort the rain leaks, hoover the dust from the bilges.
 
Just left Coral Wind with a slight drip which could build up over the 2 months until I get back. She is in the Marina but shore power is off, however the solar panels will keep the batteries topped up to cope with a few litres a day if need be.
I suppose an alarm would be useful in some situations.
 
ghostlymoron said:
I've heard the a single drip is 1ml. I think you'll be alright Peter.
Click to expand...
Ahh.... but..... drip rate was not mentioned!
As a matter of interest I ( temporally) removed the dripless seal whilst working on it. The flow through the cutlass bearing was around one litre per minute the pump managed this no problem but how long the battery would last needs more calculation. I think consideration has to be given to limit the pump fluctuating between on and off as well.
 
lw395 said:
I don't think they have much role on a typical GRP yacht, where the most likely thing they will do is pump oily bilge water into a marina.
That's fine as in £1000 fine, do not pass go.
They won't cope with a big leak like a failed skin fitting.
If you have rain getting in and being pumped out regularly, your boat will be damp and manky.
Sort the rain leaks, hoover the dust from the bilges.
Click to expand...
You make a good point. :encouragement:
 
ghostlymoron said:
I've heard the a single drip is 1ml. I think you'll be alright Peter.
Click to expand...

1 ml is a very big drip!

The trouble is, this time of year it doesn't take too many ml to make the air in your boat 100% humidity, then it's a short road to condensation and MAB syndrome.
But with good ventilation it probably evaporates before even reaching the bilge?

The worst thing to truly sort out seems to be rain running down the inside of keel stepped masts.
I sealed mine at the bottom and drained the water out every week or two, rather than have it running into the bilge.
There must be a better answer to this?
 
I have a bilge alarm and my phone number stuck in a window. I hate auto bilge pumps because of the live wires in the bilge, FVs are not as dry as yachts, evidently. My alarm has the negative running through the bilge switch. If I used one I would be inclined to include a strobe in the circuit so at least someone could see if the thing was running excessively. Of course in port there are passersby.
 
An automatic bilge pump is vital on my Sadler29. The boat (bilge keel) is on a drying mooring but sometimes sits a little nose down. In this situation, if it rains heavily, quite a lot of water gets in via the cockpit liferaft 'coffin' (or 'bathtub' if you prefer:D).

Sadly in my experience ALL float switches seem to unreliable to a greater or lesser degree. Worst culprit by far has been the WHALE solid-state switch which failed miserably last year and resulted in considerable internal water damage to the yacht when I was unable to check it for several months. (the encapsulation potting of the switch had failed around the edges).
 
VicMallows said:
Worst culprit by far has been the WHALE solid-state switch which failed miserably last year and resulted in considerable internal water damage to the yacht when I was unable to check it for several months. (the encapsulation potting of the switch had failed around the edges).
Click to expand...
I have been having problems with the Whale Orca 1300. It auto switches on but won't switch off. So I rang them and was told that it had to be mounted at an angle so that the solid state detector was higher than the outlet !
So why didn't they design the base that way? !!!!
I've reinstalled it with a couple of bolts protruding at the detector end and it now works.
 
ghostlymoron said:
I've just read in another discussion that it's common to wire an auto bilge pump direct to the battery. I've had a boat wired like this but would it really save your boat if there was a catastrophic leak? A decent sized pump draws quite a bit of juice so would flatten the battery in no time.
It may work in a marina with a sharp eyed attendant but not on my mooring in an unattended lagoon. I'd just sink with a flat battery.
Click to expand...

I guess if there was a slight leak you might be pleased the bilge pump had kicked in now and again and prevented damage to the interior of the boat, or the engine - or worse.
As for the boat sinking with a flat battery .... I don't see how that is any different to the boat sinking with a fully charged battery .
 
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