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Steve Olson · 25-11-2013, 12:04

I woke up to hear my bilge pump running. I inspected the bilge to find enough water inside to properly activate the bilge pump float switch and the pump was spinning, but not pumping water out of the bilge. I disconnected the exit tube from the pump and found that the pump appeared to be working properly and was pumping water with what seems to be a sufficient amount of force, so I suspected the exit line or through hull was blocked, so I took my garden hose and, from inside, was able to get the hose water to exit the boat quite easily.

This is not making sense to me. If the bilge pump is pumping out water with force and then I'm able to get water from the garden hose to force water through the exit tube and out of the boat, how is the pump not able to pump the bilge water out?

Boat: Hunter 34. Bilge pump: Rule 1500.

Vasco · 25-11-2013, 12:17

Did you try it again after flushing with the hose?

sailorboy1 · 25-11-2013, 12:31

Did you try using the hose to fill the bilge with water to see if it really pumps?

Could that the float is just stuck and the pump is not really pumping at all at the water level.

captain58sailin · 25-11-2013, 12:41

Sometimes your impeller on the pump can get loose on the spindle, it will spin the impeller around, but it slips when the water pressure is applied. It would be something to check if you are sure there is no blockage.

Steve Olson · 25-11-2013, 12:52

Quote:

Originally Posted by Vasco

Did you try it again after flushing with the hose?

Yes, and it still doesn't work.

Steve Olson · 25-11-2013, 12:53

Quote:

Originally Posted by sailorboy1

Did you try using the hose to fill the bilge with water to see if it really pumps?

Could that the float is just stuck and the pump is not really pumping at all at the water level.

Yes, I filled the bilge up w/ enough water that it clearly should have been pumping water out, but still doesn't.

Vasco · 25-11-2013, 12:57

It does not have enough force to push the water out the whole distance. When you took the outlet hose off the pump water came out with what seemed like enough pressure. Clearly it was not enough pressure. I would take the pump apart and check the impeller.

CaptFrankM · 25-11-2013, 13:04

Steve,

I am going to make a couple of educated guesses here. Please let me know if I am wrong on either of them.

The first is that you did actually put the pump back in place and try to run it again after taking it apart. Therefore, even though you flushed the system and checked the pump outflow, it is still not working.

The second is that this is not a new boat or a new bilge pump. It is really just a guess there, but I would assume if either of those were true, you would have said so.

However, I am going to first ask when the last time you are absolutely certain that the bilge pump was pumping water over the side? Have you ever confirmed that it did that?

I am going to say that your fundamental problem is that your pump is experiencing too much head loss. That is generally the only problem that would give the symptoms you are describing. A centrifugal pump, like the Rule you described, will pump fine if there is no pressure for it to pump against. But, if there is any resistance to flow, the pump may not be able to overcome it. This can happen with something as simple as having to pump the flow up too high a distance. A Rule 1500, for example, will pump 1500 gallons with no hose attached to it, but force it to pump up 6 feet from the bilge to the thru hull and output drops by more than half.

Add an obstruction to the line that increases resistance but doesn't fully block the line and it drops even more.

Now add in a little corrosion on the wiring so that the pump isn't getting a full 12 volts of power, but is only getting 10 volts, for example, and the pump which was going great guns with no hose connected (or a short hose only a foot or so up) will be unable to overcome the forces working against it.

Unfortunately, there is no easy fix for this. You can replace the wiring and clean all of the connections, replace the output hose with all new line and increase the size of the pump to make up for the length of hose that the pump has to work against. Any of these might fix the problem, all of them probably will.

Steve Olson · 25-11-2013, 13:12

Quote:

Originally Posted by captain58sailin

Sometimes your impeller on the pump can get loose on the spindle, it will spin the impeller around, but it slips when the water pressure is applied. It would be something to check if you are sure there is no blockage.

I seems to be working, even when I partially block the pump's output to put back pressure on it.

sailorboy1 · 25-11-2013, 13:20

It is an impeller or a motor problem. Either the impeller isn't firmly attached to the shaft and is slipping, or the motor is not turning at full speed.

Those are the only things that would stop it from pumping if there isn't a clog.

Time for a new pump.

scoobert · 25-11-2013, 13:26

Replace the pump first. Then go further.
At worst, you end up with a spare pump.

Steve Olson · 25-11-2013, 13:28

Quote:

Originally Posted by CaptFrankM

Now add in a little corrosion on the wiring so that the pump isn't getting a full 12 volts of power, but is only getting 10 volts, for example, and the pump which was going great guns with no hose connected (or a short hose only a foot or so up) will be unable to overcome the forces working against it.

LIGHTBULB!! My battery bank was low and not putting enough current to properly power the pump! I'm new to boat ownership, but surprised that I didn't consider this…durr!! The amount of things to know when it comes to owning a boat is a bit intimidating…but I'm learning!! Thank you so much!!

Steve

CaptFrankM · 25-11-2013, 13:35

Steve,

Another possibility occurs to me. Does your output hose happen to have a check valve in it? Some installations have a check valve to prevent back siphoning through the thru hull while heeling. If your system does, it may be sticking.

A Rule 1500 pump with zero head has an output pressure of about 15 pounds, I think I remember reading. City water pressure generally runs between 50 and 70 pounds. It's possible that, if you have a check valve, it might not be opening at the lower pressure.