Bilge Pump Running But Not Pumping

[Scout 30]

I came back home from evacuating for Irma & my Whale Supersub was running but not pumping. I jerked on the hose & it started pumping. Any idea what would cause this?

[rwidman]

Originally Posted by Scout 30

I came back home from evacuating for Irma & my Whale Supersub was running but not pumping. I jerked on the hose & it started pumping. Any idea what would cause this?

My first thought would be debris blocking the hose.

[Scout 30]

I checked that & there was no debris that I could see. This is actually the second time it's happened. Pretty disconcerting.

[Terra Nova]

Perhaps a poor installation with traps in the line?

[rwidman]

I once had the impeller become disconnected from the motor shaft. The motor would run but the impeller did not and the pump did not pump.

Of course, tugging on the hose would not have fixed this.

I used epoxy to reattach the impellor but replaced the pump. The original is now a spare.

[rwidman]

Is there a check valve somewhere in the discharge? There shouldn't be so if there is, remove it. A check valve can jam or be jammed by debris.

[John_Trusty]

Centrifugal pumps are very simple, so there must have been a blockage in either the input or the output. Since you cleared it by 'jerking' on the hose, you must have dislodged an output blockage. They do not build up much pressure, so it was probably a small blockage that it could not clear. Do you have the inlet filter installed on your Whale Supersub?

Most manufacturers run bilge tubing using wire reinforced vinyl tubing as it is very flexible, cheap, and easy to install in the turns between pump and through-hull. The wire reinforcing presents impediments to flow and allows more blockages. A general improvement for most boats is to replace the outlet tubing with smooth-wall rubber tubing of equal diameter. This is a fun job, considering where the tubing runs, so I recommend flashlights, a box of bandaids, and a thesaurus for cuss words!

[ZULU40]

stuffed impeller I would say

[Nightcrawler]

Had a similar issue with a Rule pump. It was cavitating. Every now and then it would start up and cavitate, running, but not pumping. Plenty of water over the impeller. I replaced the float switch and that solved it. I think the switch was coming on with too little water, setting up the cavitation. Just a guess, but it worked.

[S/V Alchemy]

Hole in the hose covered with tape that adheres well enough when you accidently touch it to restore function temporarily.

You can guess how I know such a specific cause.

[wjhutchings]

Originally Posted by Scout 30

I came back home from evacuating for Irma & my Whale Supersub was running but not pumping. I jerked on the hose & it started pumping. Any idea what would cause this?

I hope it wasn't dry for too long as all pumps use the fluid they are pumping as a coolant and in the case of centrifugal pumps as a lubricant as well, if I was you as a just in case I would at least strip the pump down and look at the impeller to make sure there is no damage, better that than have the pump fail on you when you most need it

[Scout 30]

Originally Posted by Nightcrawler

Had a similar issue with a Rule pump. It was cavitating. Every now and then it would start up and cavitate, running, but not pumping. Plenty of water over the impeller. I replaced the float switch and that solved it. I think the switch was coming on with too little water, setting up the cavitation. Just a guess, but it worked.

This is actually what it sounded like. The float switch is built into the pump on the Supersub so I can't change that.

[Scout 30]

Originally Posted by wjhutchings

I hope it wasn't dry for too long as all pumps use the fluid they are pumping as a coolant and in the case of centrifugal pumps as a lubricant as well, if I was you as a just in case I would at least strip the pump down and look at the impeller to make sure there is no damage, better that than have the pump fail on you when you most need it

The pump was actually under water while it was running.

[amanoni]

If the pump is a diaphragm type (many are) the intake or outflow "flapper" may have something lodging it open. If you have a quick disconnect type fitting, take the hose off and check for debris at those two spots. Make sure the flappers function properly. Reconnect then give it a try.

[CShawn]

Originally Posted by John_Trusty

... This is a fun job, considering where the tubing runs, so I recommend flashlights, a box of bandaids, and a thesaurus for cuss words!

Lol! Having done this on a 1980 Catalina 30 with the help of my 30 year old son, I can concur with this assessment, but I forgot to bring the thesaurus and was forced to repeat only a few many times.