Bilge pump fuse blowing

[Ricco1]

I have a second bilge pump on my boat, teamed with a float switch. It's been getting some use as I've a leak where the bearing right at the back of the boat screws into the stern. This will be fixed over the winter, when the boat will come out of the water.

 

Anyway I noticed yesterday that the pump hadn't come on when I expected it to. The obvious culprit was the fuse and sure enough, it had gone. I replaced the fuse, lifted the float switch. The pump ran for half a second before the fuse popped again.

 

My initial thoughts were that the pump was probably blocked with debris. Got it out and although there was a hell of a lot of stern gland grease around it the impeller seemed reasonably clear.

 

I'm wondering now whether my connections are the problem. I recycled the pump from another boat, the remaining wires were quite short. I joined the existing wires to longer ones to reach the fuse then battery with crimp connectors.

 

Would damp/ water around unwaterproofed crimp connections tend to blow a fuse, or is it more likely that the muck around the pump is the reason for this? Pump draws 2 amps, fuse is 5 amps.

 

Thanks

[The Bagdad Boatman (waits)]

have you looked at adding more stern gland stuffing, that can be done in the water. Loosen the stern gland bolts, slide the clamp back and put more packing round the shaft then tighten up. The pump sounds to be at the end of its life.

[Martin Megson]

 

Would damp/ water around unwaterproofed crimp connections tend to blow a fuse, or is it more likely that the muck around the pump is the reason for this? Pump draws 2 amps, fuse is 5 amps.

 

Yes if the connections aren't waterproof then water could cause them to short out and blow then fuse.

[dor]

 

Would damp/ water around unwaterproofed crimp connections tend to blow a fuse, or is it more likely that the muck around the pump is the reason for this? Pump draws 2 amps, fuse is 5 amps.

 

Yes if the connections aren't waterproof then water could cause them to short out and blow then fuse.

 

 

Enough to blow a five amp fuse? I doubt it, even if they were fully immersed.

 

Assuming the impeller is clear then I suspect the fault is within the pump itself.

[by'eck]

If pump is running ok and doesn't appear blocked, try a 10 amp fuse.

[Arthur Brown]

Automotive fuse or glass body fuse?

Make sure that the fuse is T rated. If your supplier doesn't understand then they are not T rated.

A "T" rated fuse will hold up for a short time during switch on surges, F rated fuses blow very quickly, FF rated fuses blow extremely quickly -they are intended to protect semiconductors.

[Chewbacka]

Have you measured the running current as it was not clear if 2amps is actual or specification.

[Ricco1]

Update on this: I cleaned everything up and renewed the crimp connections. Ran the pump from a spare battery, no problems. Put it back in the bilge of the boat and connected the wires to the batteries. A few buckets of water in the bilge had the float switch lifting up until it kicked in. The pump ran for a minute or so before cutting out, the fuse had gone again. Replaced the fuse with a 10 amp one, this blew immediately.

 

Is it likely that the pump is knackered?

[Paul C]

It sounds like the pump is either end-of-life or you've not cleared it out properly - is it possible to access its impellor and freely spin it with your hands? If not then there's either something in it, or the bearings/something else has gone in it. Just as a sanity check, is the pipe from the pump to the outlet clear?

[Arthur Brown]

Running current usually doesn't account for bits in the bilge jamming the pump, does it have the correct strainer over the inlet?

 

If a 10a fuse blows IMO try a new pump.

[Ricco1]

It sounds like the pump is either end-of-life or you've not cleared it out properly - is it possible to access its impellor and freely spin it with your hands? If not then there's either something in it, or the bearings/something else has gone in it. Just as a sanity check, is the pipe from the pump to the outlet clear?

 

Yes the impeller span freely when I cleaned the pump up. As far as I know the 'exhaust' pipe is clear. Certainly, the jet of water coming out of the back when the pump was running was as I expected it to be.

[Paul C]

It could be a stray path to the hull (short circuit) from wiring somewhere else, its worth looking at the wiring carefully. Obviously, its also worth making sure any connections are suitable quality for a wet (but not submersed) environment. Heatshrink is handy here, especially the stuff with adhesive inside.

[Midnight]

Update on this: I cleaned everything up and renewed the crimp connections. Ran the pump from a spare battery, no problems. Put it back in the bilge of the boat and connected the wires to the batteries. A few buckets of water in the bilge had the float switch lifting up until it kicked in. The pump ran for a minute or so before cutting out, the fuse had gone again. Replaced the fuse with a 10 amp one, this blew immediately.

 

Is it likely that the pump is knackered?

 

How long did it run on the spare battery?

Was is submersed same as when in place?

Were the crimped wires under water during the test?

 

I'm wondering if the pump has an internal leak which would blow the fuse. Even so given your issues with leaking gland I would suggest time to replace it.

[FORTUNATA]

I have a second bilge pump on my boat, teamed with a float switch. It's been getting some use as I've a leak where the bearing right at the back of the boat screws into the stern. This will be fixed over the winter, when the boat will come out of the water.

 

Anyway I noticed yesterday that the pump hadn't come on when I expected it to. The obvious culprit was the fuse and sure enough, it had gone. I replaced the fuse, lifted the float switch. The pump ran for half a second before the fuse popped again.

 

My initial thoughts were that the pump was probably blocked with debris. Got it out and although there was a hell of a lot of stern gland grease around it the impeller seemed reasonably clear.

 

I'm wondering now whether my connections are the problem. I recycled the pump from another boat, the remaining wires were quite short. I joined the existing wires to longer ones to reach the fuse then battery with crimp connectors.

 

Would damp/ water around unwaterproofed crimp connections tend to blow a fuse, or is it more likely that the muck around the pump is the reason for this? Pump draws 2 amps, fuse is 5 amps.

 

Thanks

I've had fuses blow. 2 nights ago I plugged in my small Argos DVD player and it was dead. A feeling of dread came as I wondered if I'd be spending the night without being able to watch a movie. Then I calmed down, took off the plug and the 3 Amp fuse had blown. I replaced the fuse and then it was fine.

 

If your fuse blows then you have excessive current. Do you have the right wire diameter for the pump? Does the pump have a watts marking on it? If so, divide 12 volts into that figure and it will give you the current. For example, a 20 watt light at 12 volts will give just over 1 amp. Whatever the current is, the wire must be of suitable size and the fuse must be rated to the wire. Especially where there's a motor and inductance involved.

 

One thing you can do is try and find out how much current is being drawn. If you put a multimeter in series with one of the leads to the pump, it will give you the current. It's very important, though, the meter isn't limited to just 10 amps (as mine is).

 

It sounds as if you're getting large inductance currents or a surge. Check all the connections are clean too. even the battery terminals and clamps. Test with power off and a meter on Ohms to see if you get 0 on the 2000 K marking from removed battery clamps and pump lugs. Possibly remove the pump and bench test it to see if it works O.K. out of the system.