Installing big pump to deal with large boat leaks

[jfm]

I had this idea of fitting a big pump to bail the boat out. My logic is, if I got a busted seacock or some other failure it would be a shame to lose the boat and spend a few days in the liferaft just becuase the poxy stnadard bilgepumps couldn't bail out fast enough, when big pumps aren't expensive.

So I'm thinking of fitting one of these, though I have a glitch and would appreciate ideas

My thinking is that if I get a big leak I'll know early, long before the genset is soaked, becuase lots of alarms go off. So I start up the big pump, powered by generator, and hey presto. Machine Mart sell nice roll-up discharge pipe for the pump outlet (like firehose) and the pump can be installed in engine room and also lifted out quickly to somewhere else, eg if there's a big leak up forward

The flow rate on this pump at very small heads is something like 700litres/minute. That's at the top of the range - this is a 3hp motor job and to get bigger flow rates you need a seriously big pump. A domestic (600mm) washing machine/diswasher (how my brain thinks of these things...) is 300litres volume (600x600x850) so this pump would shift just over double that volume, say, every minute. Not bad, you'd think.

But then I found this table on the net. It says with a 3inch hole (that's the engine cooling intake seacock) and a 4 foot head (that's the waterline level to the keel, where the engine raw water intakes are) the water will flow at 350 (US) galls/minute, which is about 1300 litres a minute.

So the 3hp big Clark pump will only move half the required water and I'll sink in 20minutes rahter than 10. Great. And the Ferretti idea of a Y valve and using the engine raw water pumps isn't any use at all, cos those babies don't pump anything like 1300 litres a minute

So you have pretty much no hope of outpumping a 3 inch dia hole in the boat. You have to use those hammer-in wooden bungs, or dive in to put a sheet over the outside of the hull to cover the hole. No feasible pump will save you.

Have I missed something in the analysis? Am I being too pessimistic? I'll get the pump anyway cos it'll be handy in a fire and it can just about tread water against a 2inch hole (toilet seacock), and, er I just fancy one anyway. Anyway you lot have good ideas. Anything better to suggest that this pump?

 

[MapisM]

I guess your Volvos aren't fitted with PTOs, are they? If they would, with 800 ponies each, you could connect a couple of pumps big enough to empty the whole med in a matter of minutes... /forums/images/graemlins/grin.gif
But the Y valve is not a bad idea anyway.
If you're embarking water due to an engine cooling intake seacock gone bust, we don't want to cook the engine while the huge pump driven by the engine itself is doing his job, do we?

 

[Seanick]

Preventatve maintenance and look where your going! /forums/images/graemlins/grin.gif

 

[hlb]

Yep, think you must be missing sumat. When my prop shaft ripped out the stern gland (which disintigrated) It left a 5 to 6" hole, with the prop shaft sticking through it. I managed about a mile back into Salcolmbe where the inshore life boat met me with two little petrol pumps. Little Strimmer type motors. Anyway as long as I was going forwards it did not leak to much and was only about 4ft deap /forums/images/graemlins/blush.gif Then the bigger pump they had brought to the pontoon, seemed to keep up.

No idea if this helps.

Have you thought of a submersible pump you can just chuck in the water.

 

[Nick_H]

I haven't done the maths, but comparing size of a 3 hp outboard (small) and a 13 kVA genny (big), surely you can just fit two pumps and the genny will cope easily. I know there's loads of losses to build into the sums, and generators are particularly inefficient, but are you saying the genny couldn't cope, or is there another reason why two pumps doesn't work?

 

[jfm]

Hmmm. That's interesting. It suggests that I wont really get 1400 ish litres/minute (nearly 5 washing machines, in volume terms) of water thru a 3 inch hole. That figure did seem a bit high. In which case, the 3hp 700litres/minute pump ought to do some good. Hmmm

As your boat got quite deep with water inside, it could be the head ifference between the inside water and the outside sea was down to a foot or so, which would cut the water intake rate dramatically. My doomsday 1400litres/minute is at 4 foot head, which wouldn't be there for long as the boat filled up

That Clarke/Machine Mart catalog has submersibles and yes I might get one of those instead. The biggest is this, but I'm suspicious cos it claims almost the same flow rate as the other one yet is is 600w motor compared with 3 horsepower. Doesn't stack up. Praps get 2. Or stop worrying

But thinking about it HLB, having lived thru a dreadful day where you took on much water, knowing what you know now, would a big chunky 3hp pump have helped you on that day? If you had that day again (heaven forbid!) would you want to have a big 3hp pump with 3 inch hoses? Or would it have been a waste of time gimmick?

 

[jfm]

No prob with power. The genset 17.5kva gives out 75 Amps, that 3hp pump drawa about 10amps, so you could run 7 of them. Ok there would be "overheads" running on the boat and perhaps not time to switch em all off but you'd have no prob at all running say 3 of those pumps. 3 pumps and hoses is a lot of gear to stow and carry though. I'd prefer just one pump, but come to think of it the best answer might be to carry two of the submersibles linked to in my reply to HLB above

 

[jfm]

Yup but you could use that argument to say don't carry a liferaft! I'll do my best never to get a 3inch hole in the boat but it is at least possible, ask HLB, and the many other slowly sinking boats posted on here time and time again. It would be a shame to have to resort to liferaft or even just lose the boat without any danger to lives, for want of a £300 pump!

 

[hlb]

Think what helped me, was my hole was at the back, so as long as I was going forwards, it slowed the leak. Bit like auto bailers in a dinghy. Could not do much to block my hole, cos it had the prop shaft running through it. Anyway I could not drive the boat and try to bung up hole at the same time. Suppose it depends how far out you are.

Think a sea cock would be different. The faster you went, the more water you would drive into it. On the other hand it would be easier to bash some thing into the hole.

I think you just cant deal with all eventualities and who wants to carry all the possible gear you might need. Probably never find it anyway, under the rest of the must have stuff.

 

[acbruce]

I must admit to having thought about this myself. My problem is that the service batteries on the boat are in a container between the engines and thus not very far above the bilges. About stern gland height in fact. So good for weight distribution but the first things to be submerged. So in order to install a pump I will need to instal a seperate electrical system for the genny and the pump.

It's a pretty silly design on the Beneteau and as there is only one small manual pump a water ingress of size would cause a big problem very quickly! Your post has made me think that I ought to do something about it!

 

[nimbusgb]

A yacht I sailed on once had a centrifugal pump with 2 inch inlet and outlet rigged via a mechanical clutch to the main engine. The pump could draw water either from a seacock for fire fighting ( or really fun water fights ) or a strainer in the bilge.

Still baffles me why more boats don't have this sort of arrangement. Compared to some 12v piddling pump in the bilge these are real industrial units up to the job!

Just BTW the boat was 60' , of wooden construction and in need of some maintenance. The engine bearers were bolted to the bottom planks and as the boat rolled over swells the engine weight 'eased' the bottom planking and the joints seeped water visibly. We used that pump to clear the bilge twice a day on the journey from Mauritius to Durban!

/forums/images/graemlins/laugh.gif

 

[hlb]

Having said all that, I think a sensible sized submersible pump, might be usefull in putting out fires or even washing the boat. At least it would be good for water fights, so get one. /forums/images/graemlins/grin.gif

ACB. Believe it or not, batteries will work under water, as will electric motors. I got about two days out of mine before stuff started to fail.

 

[jfm]

Nope, no PTOs fitted. They could be fitted, but considerable cost.

Maybe I'll fit the Y valves anyway,

cos it is a simple job and the engine pumps could help the 230v pump in an emergency. By the time you have bought 2 valves, 6 hose tails, jubilee clips, it is easily £300 so the same price as a pump!

 

[jfm]

But I think it's crucial to have an alarm that sounds if there bilge has more than a teaspoon of water, so you can get the gen (and engines) started before the batteries see any significant water. Once started the genset and engines should be fine, and then you can set up the pump

I'll think about it, but I'm inclined to get the Clarke submersible pump, and the Y valves on both engines, plus I carry the wooden bung things and a hammer, and leave it at that. Otherwise I'll get called Happy1

 

[Pinnacle]

[ QUOTE ]
....... plus I carry the wooden bung things and a hammer, and leave it at that. Otherwise I'll get called Happy1

[/ QUOTE ]

We don't want that!!! /forums/images/graemlins/shocked.gif /forums/images/graemlins/shocked.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[NorthUp]

Buy yourself a cheap portable Honda 3" petrol driven pump, or even a Chinese copy from ebay for around £150.
Advantages- you will keep pumping right up until you have to step off your sinking boat into a liferaft or other boat.
You can pump far more water than a 2" electric motor driven pump.
You can use it to fight a fire- on your own or another boat.
You can pump out someone elses boat.
You will win almost every water fight.
disadvantages- keep a gallon of fuel in a can, not in the pump tank, so you can rotate stocks every couple of months (put it in the mower?)
more awkward to stow, but how big is your boat?
Petrol/ diesel portable pumps are now required to be carried aboard fishing boats over around 17m by the MCA, and have saved at least 2 or 3 in the last year alone.

 

[bazobeleza]

Why not look at the machinemart petrol powered version 925 l/min with a built in honda 4 stroke engine at £350 seems a b'm toying with idea myself if only for deck washing, squirting the kids and firefighting, easily stowable and can be moved to where its best needed. just ad a couple of flexible hoses.

 

[hlb]

After numerous near do's at sinking, I got fitted bilge alarms. Mind the alarms cause more trouble than the bilge pumps and switches, which tend to fail the first time you get a leak.

My main concern was not sinking whilst on the boat, but say a little leak from stern glands (Always) and a bilge pump packs in. I got a big claxton thingy, that would wake the whole marina. Float switches are fairly useless, I've had them fail in days.

 

[Nautical]

If you need (God forbid) to shift that sort of influx you'll need something like a trash pump ... Here

We used to carry one and can confirm will keep fairly big hole from doing its worst to ruin your day !. Tough as ole boots and can handle a fair amount of seaweed and general [--word removed--] floating about without bunging it up.

Handy too if you need to transfer to another vessel in similar bother or use as biggum fire hose.

 

[jfm]

Hmmm that's food for thought. I was thinking elec motor more reliable than a petrol engine that hasn't been run for a while (might not start, I mean) but I see from the machine mart site that it is easy to get 1000litres/min from a petrol powered one. And they're not expensive, as you say. £380 with a honda 5.5hp 4 stroke. Petrol can be rotated with tender so that part is easy. Takes up quite a bit more space than electric but I think I can fit it in. Hmmm, will think about that, thanks