Strange manual bilge pump behaviour

[Slycat]

Hi all,

I'm thinking this means the pump has broken somehow but just in case..

Manual bilge pump mounted in cockpit with fairly standard up and down lever for pumping.

When I pump I can hear air moving through the system. No water pumped.

If I remove the tube on the 'out' side and pump.... no water, just air movement sounds

If I hold my palm against the 'outlet' and create a seal, it pumps water well and it squirts out against my hand.

Any thoughts? Does this mean an internal seal has gone and by creating an additional seal it's compensating for the problem (i.e. pump dead) ?

Thanks for any insight !

 

[NickRobinson]

Could be the outlet vale needs cleaning. Your hand is allowing the diaphragm to suck water..

 

[captainboo]

It would suggest that the outlet valve is either stuck open by debris or permanently deformed such that when you pump it normally without your hand over the outlet the suction that should be created by the pump is not closing the outlet valve. Placing your hand there prevents air going into the pump the wrong way and is allowing the pump to work normally and lift the water up.

Best bet, depending on the pump, would be to remove and overhaul, replacing the valves if required.

 

[lw395]

Completely normal!
Obviously not ideal, but very, very common.
The valves work poorly when dry, a bit of bilge dust makes it worse.

I've raced open boats that rely on their pumps. You soon learn to install them where you can put a hand over the outlet while pumping.
Otherwise pumping the air really fast is your best hope.

 

[William_H]

I assume you mean the common diaphragm type pump where your up and down movement is converted by levers to pushing in and out a rubber diaphragm. The other alternative is a pump with a tube on the outside and a piston pushed up and down.
This latter type can have a lot of friction in the seals of the piston if it is sealing properly and if not it won't lift water very well.
The diaphragm type is far more common these days made of plastic with rubber diaphragm and flap valves. They can handle some debris. If it is this type you need to dismantle the pump. The operation will become clear with flap valves on the inlet and outlet. If it is clean and flaps seem flexible then it should work well. good luck olewill

 

[Slycat]

Thanks guys, seems it could be just an issue of cleaning so I'll take it off and have a look before ordering a new pump.

Thanks for the tips.

 

[MonniotC]

If it's a normal Whale/Henderson type bilge pump, a service kit contains new diaphragm and valves/seals etc. Unless the pump is physically smashed to bits you should never have to buy a new pump.

 

[Dockhead]

If it's the very common and expensive Whale Gusher 10, then you have the classic valve seat rot.

These pumps are made out of die cast alu, and are merely painted, not powder coated, so the valve seats rot out if any sea water is left in them. Total crap design.

I went through this with mine a couple of years ago -- wasted a whole day pulling it all out, carefully sanding it smooth, then painting it as well as I could with proper aluminium primer and hammerite.

It is still working ok but I am now careful to never pump sea water with it, and rinse it out thoroughly after every use. I killed it by pumping seawater out of my engine room bilge after letting sea water in whilst cleaning sea strainers. But it doesn't take sea water to kill them -- I think the valve seats will rot eventually no matter what.

Best solution is to bin it and buy one made out of plastic, with rot-proof valve seats. Failing that, you are in for a day fixing it like I did mine. If you have time for it, you might improve on the original construction by having the whole thing powder coated, or better yet, hard anodized, which should considerably improve resistance to corrosion. But query whether binning it and replacing it with a proper plastic pump would be less trouble, and possibly even cheaper.

Good luck!

 

[Kukri]

Yes; the Henderson Mark 5 (made by the same people!) is a better pump in every respect.

 

[lw395]

The plastic pumps frequently exhibit the exact same behaviour.

 

[Slycat]

Thanks for the tips all. Took the advice and took the pump apart and rinsed with fresh water. Was quite messy inside with some evidence of corrosion making up most of the mess.

After dismantling and rinsing, all works well.