Fresh Water Pump continues to cycle

ric992

ric992

Member
Apr 5, 2021
147
Miami Beach
Boat Info
2007 Sundancer 48
Engines
Cummins QSC 8.3
Hi, my water pump continues to try and pump very slowly. then will over heat and stop. When I first turn it on it builds the initial pressure then stops as normal. As soon as I first use any water then it will continue to barely run until gets hot and stops working at all. Is it completely broken or is there a way to fix? I thought about running some CLR diluted thru the system? Any advice, should i just replace the pump?
 
You probably have some debris in the valves that causes it to take a long time to build pressure, and then leak down that pressure if it ever gets to the point of shutting off, only to have to turn on again.

You can usually disassemble the head (carefully, noting where all the parts go) and clean it and reassemble and it will be fine.
 
Not just the head... a fresh water pump will cycle when there is a leak somewhere in the system (assuming all faucets are off).

Could be anywhere... leaking faucet(s), head, plumbing.
 
Hi, thank you for the responses. I don't think there is a leak anywhere since it doesn't start until after the initial pressure build up and after a faucet is turned on then off..I will try and disassemble and see if any debris is in the unit..Is diluting some CLR into system to run thru a bad idea? maybe some calcium buildup...this is the original water pump for a 2007
 
ric992 said:
Hi, thank you for the responses. I don't think there is a leak anywhere since it doesn't start until after the initial pressure build up and after a faucet is turned on then off..I will try and disassemble and see if any debris is in the unit..Is diluting some CLR into system to run thru a bad idea? maybe some calcium buildup...this is the original water pump for a 2007
Click to expand...
Not a horrible idea, just probably useless. If you dilute it enough, it's not going to take care of a hard deposit. If you don't dilute it enough, it may take quite a while to get the taste/smell out of the system.

Wonder how long it can sit after that initial pressure has built up? Does it eventually start running on its own to rebuild pressure? If not, then may not be those valves as they would tend to leak a little bit over time if they have crud in there.
 
I'm going to suggest that your pump is cooked. You can run a properly functioning fresh water pump continuously without it overheating. Every other year I run a full 100 gallons out of my tank, non-stop. It takes over an hour. The pump has no issue with this, nor should it.

On the pressure/blockage discussion - have you run your boat hooked up to dockside fresh water (via a hose)? You can determine if you've got blockage someplace, independent of your pump, by using dockside water.
 
And hey on the CLR idea - 99% of your freshwater system is plastic. If you had water hard enough to form deposits in your faucets I think you'd see horribly stained sinks and heads too. Some obvious indication of wicked terrible hard water...
 
I would first suspicion the pressure switch failing to shut off at the predetermined pressure and the pump continues to struggle to pump against a head pressure beyond its' design, causing the heat build up. Put a pressure gauge in the system and see whats going on there.
 
Last edited:
I turned off all water switches at the main terminal. The pump continues to barely pump..yes I guess pressure switch is shot. I will replace the pump, (since I already have a backup) and order the one off Amazon for the new backup one. This is a silly question, but do I need to run tank pretty close to empty to unhook and replace the pump..not to have water every where?
 

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Pinch the feed line flat with a clamp to stop the flow, if it is a flexible line. If it is a hard line just let it drain into the bilge.
 
ric992 said:
I turned off all water switches at the main terminal. The pump continues to barely pump..yes I guess pressure switch is shot. I will replace the pump, (since I already have a backup) and order the one off Amazon for the new backup one. This is a silly question, but do I need to run tank pretty close to empty to unhook and replace the pump..not to have water every where?
Click to expand...
 
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