Bilge pump question

[RickS]

My bilge pump now works (wiring issue) and is joined to the skin fitting by two lengths of hose joined in the middle by a short piece of stiff tube on the inside of both hoses (crap description, sorry).

Sucks up water but doesn't appear to be dumping it over the side. When the pump is turned off, a lot of water just comes back out of the pump. When I disconnect the joined hoses and operate the pump, water comes out of the pump-connected hose.

Would I be correct in thinking that therefore there is a block in the hose connected to the skin fitting? I assume that it would be preferable to replace both hoses with a single hose?

Thanks

[Tracy D'arth]

Come on, you don't need help with this do you?

 

Try a new hose, its unlikely that the pump has insufficient "head" to lift the water overboard.  Got a fish in the skin fitting?

Will it pump out into a bucket close by?

[RickS]

😀 Probably not to be perfectly honest, but some problems I have come across seem so obvious that I question my solution - particularly when what I think as obvious is not so when applied to boats.

I suppose what I was mainly worried about is whether the pump wasn't lifting the water enough - |I will replace the hose a at least i will know it won't be the hose that is blocked.

Thanks

[Tony Brooks]

Bank mud or rust/blacking in the bilge pump outlet. It is a centrifugal pump so not so good better at moving a volume of water than creating a significant pressure. Try running the pump and pushing a piece of wire coat hanger down the hole.

[OldGoat]

IME most pumps sold as bilge pumps fo NBs are 'of marginal utility' - especially if there's not much depth of water in the bilge. The impellors just stir the water around.

If you want to have a dry bilge is an old curculator pump and a 1/2" or 3/4" hose as short as possible.

[David Mack]

Either a blocked hose, or the wires have too high a resistance, so under load there is a voltage drop, meaning the pump motor runs, but doesn't produce enough pressure to push the water up to the skin fitting height. The fact you have had wiring problems suggests you may still have a high resistance connection somewhere in the circuit, or maybe you are using wires that are too long/small cross sectional area for the current drawn by the pump.

[Tony Brooks]

2 minutes ago, David Mack said:

Either a blocked hose, or the wires have too high a resistance, so under load there is a voltage drop, meaning the pump motor runs, but doesn't produce enough pressure to push the water up to the skin fitting height. The fact you have had wiring problems suggests you may still have a high resistance connection somewhere in the circuit, or maybe you are using wires that are too long/small cross sectional area for the current drawn by the pump.

 

Good thought.

 

So @RickS what is the voltage at the pump connectors with the pump RUNNING.

[RickS]

David, Tony thank you. The wiring problems were at the control panel which had been disconnected when the engine was being dealt with. Bit of a nightmare behind there so got an electrician to sort the control panel out. Don't know the voltage, but will attempt to find out tomorrow with a multimeter.

In fairness, it does seem to push the water up to the join between hoses, which is not much lower than the skin fitting - certainly over half the height.

Will get back to you re: voltage

Thanks

3 hours ago, OldGoat said:

IME most pumps sold as bilge pumps fo NBs are 'of marginal utility' - especially if there's not much depth of water in the bilge. The impellors just stir the water around.

If you want to have a dry bilge is an old curculator pump and a 1/2" or 3/4" hose as short as possible.

Thanks OldGoat. I have to go with what's there until my knowledge improves, but thanks for the suggestion

[Chewbacka]

16 hours ago, OldGoat said:

IME most pumps sold as bilge pumps fo NBs are 'of marginal utility' - especially if there's not much depth of water in the bilge. The impellors just stir the water around.

If you want to have a dry bilge is an old curculator pump and a 1/2" or 3/4" hose as short as possible.

The reason they leave a layer of water behind is because they are cheap centrifugal pumps, but there are a couple of advantages, namely the pump doesn’t run dry and any oil or grease in the bilge will float on top of the remaining layer, and not be pumped into the canal.

[Tony Brooks]

To clarify, centrifugal pumps can run dry for far longer periods before damage occurs, if it occurs at all and they can handle a degree of solid particles better than many other type of pump. Then there is the question of designing any type of pump or inlet that allows the bilge to be pumped totally dry. Fit the inlet tight against the bottom of the boat and it would not be able to draw much water in and would probably block around the edges with muck. The only way around it with whatever type of pump is to arrange a small well at the lowest bilge point and pump from that so the bilge area is dried but even then water will be left in the well base. My boat has one that was formed by a cutout in the base plate that was covered on the outside by the skeg. Even that was to totally satisfactory because even a small list stopped all the water draining into the well.

[blackrose]

How much water did you try to pump out? Perhaps if you test it again with the bilge pump dunked into a full bucket of water it will pump overboard. You'll never get the last inch or so out as that always falls back down the pipe and out of the pump as soon as it stops.

Edited February 27, 2022 by blackrose

[pete.i]

The only way to COMPLETELY dry your bilge is to get down on your hands and knees with a bucket and sponge or a mop. As said there will always be a small amount of water left and even if there are no leaks (hopefully none) condensation will put a surprising amount of water down there especially on boat that isn't lived on for long periods.. As long as the bilge pump is pumping out enough to stop your boat from sinking then it is doing it's job.

[blackrose]

5 hours ago, pete.i said:

The only way to COMPLETELY dry your bilge is to get down on your hands and knees with a bucket and sponge or a mop. 

 

 

 

Or just chuck a couple of nappies down there. Keeps mine completely dry.

[RickS]

Thanks all. Not bothered about a tiny bit of water - which I know the pump won't deal with. Happy to sponge it out - was doing that yesterday.

 

Real pain trying to get the voltage as I only have probe attachments for my multimedia and the damn thing won't keep still. I have ordered some crocodile clip leads that plug into the meter. For now I think I am just going to disconnect it, clean the pump and replace the hose, and I'll get back about the voltage.

 

Tried nappies blackrose - probably too much water in the bilge at the time as they mostly burst spilling the gel stuff all over - taking them out earlier would have been good, or only using them for the last of thewater

[blackrose]

6 hours ago, RickS said:

Tried nappies blackrose - probably too much water in the bilge at the time as they mostly burst spilling the gel stuff all over - taking them out earlier would have been good, or only using them for the last of the water

 

The only time I've ever had nappies burst when mopping up bilge water was when I threw them out of the engine hole onto the bank. They were full and had been down there for weeks - and they were the cheapest nappies.

 

As you say, they're mainly useful for getting the last half inch of water out. I've never really used them for more than that.

[Grassman]

 

My boat permanently has about an inch of water lying in the bottom of the engine bilge. The cruiser stern deck is a bad design whereby the drain hole in the bottom step into the cabin is below the waterline. I've fitted an extra bilge pump there and it does it's job of preventing it flooding.

 

I used to worry about water permanently lying there and on a weekly basis used to vacuum it out, but a reputable boat builder (a proper one who built boats from scratch) told me that the damage it's doing to the baseplate in terms of rust was so negligible it wasn't really worth the effort, so nowadays I just leave it and I no longer worry about it.

[Tracy D'arth]

20 minutes ago, Grassman said:

 

My boat permanently has about an inch of water lying in the bottom of the engine bilge. The cruiser stern deck is a bad design whereby the drain hole in the bottom step into the cabin is below the waterline. I've fitted an extra bilge pump there and it does it's job of preventing it flooding.

 

I used to worry about water permanently lying there and on a weekly basis used to vacuum it out, but a reputable boat builder (a proper one who built boats from scratch) told me that the damage it's doing to the baseplate in terms of rust was so negligible it wasn't really worth the effort, so nowadays I just leave it and I no longer worry about it.

Common on many Liverpool hulls. I have seen trays made to catch the water with bilge pumps in to dump it over the side, plumbing projects to transfer the water to the bilge pump  under the shaft etc. None seem to work 100%.

The rusting is reduced somewhat once the water loses most of its free oxygen but it can cause scaling if the area continually dries out and gets wet again.

[blackrose]

45 minutes ago, Grassman said:

 

I used to worry about water permanently lying there and on a weekly basis used to vacuum it out, but a reputable boat builder (a proper one who built boats from scratch) told me that the damage it's doing to the baseplate in terms of rust was so negligible it wasn't really worth the effort, so nowadays I just leave it and I no longer worry about it.

 

I'm not sure about that. I had water permanently laying in my stern deck lockers because there was no way to keep the water out. For years I did nothing but eventually after about 12 years I decided to do something about it. I wet-vacced them out, let them dry and got an angle grinder/wire wheel in there and drill with wire brush attachment for the corners. The pitting was horrendous. I think some of the deep pitts must have been 3mm deep. This was 5mm thick steel, but even on a 10mm baseplate I wouldn't be happy to just leave it. 

 

 

I put 3 coats of Jotamastic 87 epoxy over the bottom of the lockers and now the water can sit there for as long as it likes.    

Edited March 1, 2022 by blackrose

[Grassman]

22 hours ago, blackrose said:

 

I'm not sure about that. I had water permanently laying in my stern deck lockers because there was no way to keep the water out. For years I did nothing but eventually after about 12 years I decided to do something about it. I wet-vacced them out, let them dry and got an angle grinder/wire wheel in there and drill with wire brush attachment for the corners. The pitting was horrendous. I think some of the deep pitts must have been 3mm deep. This was 5mm thick steel, but even on a 10mm baseplate I wouldn't be happy to just leave it. 

 

 

I put 3 coats of Jotamastic 87 epoxy over the bottom of the lockers and now the water can sit there for as long as it likes.    

 

I did similar with my engine bilge a few years ago when the engine was out and access to it was easy, and found that after 20 years of continuously having had an inch of water on the baseplate there was only very light surface rust, no flaky parts and no sign of serious pitting. It was similar at the watermark on the sides of the hull.  And that's one of the reasons that these days I've stopped worrying about it.