Fresh Water Pump

[Thomv]

I have a fresh water pump that originally pumped water out of the bottom of the boat. It originally was a fresh water boat. Because I do all my boating in salt water I plugged up the inlet connection on the bottom of the hull and instead added a 12 gallon holding tank. The hose inlet for the pump is now at the top of the tank while the actual location of the pump is about half way down from the tank mounted on the plywood seat back. Because the pump inlet is now at the top of the holding tank I also ran a inner hose inside the holding tank so that the pump will draw water from the bottom of the holding tank. Now when I turn on the pump I get no water pressure but can hear the pump running. I then disconnected the inlet hose and put the hose into a quart container filled with water and then turned on the pump. Still no suction or water coming out the outlet connection on the pump no matter where I placed the full container of water. The only way I can get water to pump is raise up the inlet hose, above the pump, add a small funnel of water to the inlet hose and then the pump pulls water thru the outlet hose. Why is it not working with the other two procedures? Could the pump diaphragm be defective and not have enough suction power to pump the water thru the pump? Also are these pumps self priming?

 

[mr 88]

Name brand of pump may help. My 3 pumps are all Jabsco, and they all have impellers in them [ along with a cutting blade in the macerator unit ] and I suspect yours does as well. They should be self priming . I have one installed above my livewell with a hose that goes to the bottom of well. Never had a problem with it pulling water after it had been run dry and starting over with no priming and that entails about a 2 foot lift.

 

[dingbat]

Diaphragm pumps tend not to be self priming thus the popularity with scoop type intakes on washdown pumps.

 

[Thomv]

Name brand of pump may help. My 3 pumps are all Jabsco, and they all have impellers in them [ along with a cutting blade in the macerator unit ] and I suspect yours does as well. They should be self priming . I have one installed above my livewell with a hose that goes to the bottom of well. Never had a problem with it pulling water after it had been run dry and starting over with no priming and that entails about a 2 foot lift.

I will check on Thursday as to the brand.

 

[Thomv]

I will check on Thursday as to the brand.

Both are Shurflo pumps.

 

[mr 88]

Sounds like you have a bilge pump and as noted does not have the proper impeller for what your trying to do. Have you considered putting the pump in the bottom of the tank and running the discharge hose through the side of the boat,higher than the water line ? Other than that you have to buy a self priming pump to keep the current location of the pump/

 

[Thomv]

Sounds like you have a bilge pump and as noted does not have the proper impeller for what your trying to do. Have you considered putting the pump in the bottom of the tank and running the discharge hose through the side of the boat,higher than the water line ? Other than that you have to buy a self priming pump to keep the current location of the pump/

I don't think they are bilge pumps. Both came with the boat from the factory, one for the sink and one for the front bow shower and are mounted on the back of the seat. On a couple of occasions, both pumps were left on over night which might have caused a diaphragm failure.

 

[dingbat]

On a couple of occasions, both pumps were left on over night which might have caused a diaphragm failure.

diaphragm pumps can handle being run dry.

Ive left the washdown on more than a few times when loaded on the trailer. Walk by a day or two later and hear the pump running.

The fact that the pumps works when primed tells me the diaphragm is in tact.

 

[garbageguy]

I have a fresh water pump that originally pumped water out of the bottom of the boat. It originally was a fresh water boat. Because I do all my boating in salt water I plugged up the inlet connection on the bottom of the hull and instead added a 12 gallon holding tank. The hose inlet for the pump is now at the top of the tank while the actual location of the pump is about half way down from the tank mounted on the plywood seat back. Because the pump inlet is now at the top of the holding tank I also ran a inner hose inside the holding tank so that the pump will draw water from the bottom of the holding tank. Now when I turn on the pump I get no water pressure but can hear the pump running. I then disconnected the inlet hose and put the hose into a quart container filled with water and then turned on the pump. Still no suction or water coming out the outlet connection on the pump no matter where I placed the full container of water. The only way I can get water to pump is raise up the inlet hose, above the pump, add a small funnel of water to the inlet hose and then the pump pulls water thru the outlet hose. Why is it not working with the other two procedures? Could the pump diaphragm be defective and not have enough suction power to pump the water thru the pump? Also are these pumps self priming?

I diagram here would be helpful to evaluate your liquid storage and pumping system. These systems are simple, but require understanding of the hydraulics involved.
If I understand your situation, you had a water supply inlet somewhere below the waterline of your boat when it's in the water. And now you're in saltwater, so you aren't using the water the boat is in as a source.
You indicated "the hose inlet for the pump is now at the top of the tank? But then you say you ran a hose so the pump will draw water from the bottom of the tank. You may have created a portion of the line that is filled with gas (air) and not liquid (water), and the pump cannot compress the gas to get the fluid to move through the system. Diaphragm pumps are positive-displacement pumps, and are generally self-priming, but they have limitations, especially if the diaphragm is compromised. Even with a compromised diaphragm, such a pump might be able to move liquid through it (especially with help of some elevation head) but will have a very hard time if there is gas (air) in its supply side.

I suggest checking to see if your "inner-hose" maintains an air-pocket, and the condition of the pump.

 

[Thomv]

Today I removed the pump from the boat so that I can bench test it. I ran a water line into a 2.5 gallon water tank and then turned on the pump. Still no water coming out of the discharge side of the pump. I then took it apart and the diaphragm looks good so now I have no idea why it can't pump water. About ready to just order another pump. This Shurflo pump must be an older model because I don't see it in their catalog. Manufacturing date is 08/2007.