I have a 2008 340 Sea Ray Sundancer. I cannot get the shower sump to pump. After the box fills with water the float switch goes off and I hear the pump working but no water is getting pumped out. If I turn the float switch on and off manually after this, it will pump. If I remove the rubber check valve from the pump it will work but water keeps coming back into the pump outlet. I contacted rule and they told me if the hose going out the boat has any dips it will cause an air pocket causing this problem. There is not access to the hose going out of the boat. I have replaced the pump and float switch. Does anyone have a solution for this problem?
Welcome to the forum.
Assuming the sump box and pump have been fully cleaned and problem remains.
On my 2000 380DA over a decade ago I was having a problem w/ that system and I replaced the weird rubber check valve w/ an aftermarket plastic body part.
That system has been working fine since.
My experience / understanding is that a bilge pump will work great when no output check valve is installed, but will then drain back into the sump at shutoff, causing excess cycling. When a bilge pump has a check valve, then it WILL have problems when / if air gets into the system.
The Attwood pumps will behave like this with low voltage - the integral float switch trips and the pump seems to run, but does not move any water. Suggest testing voltage at the pump, if low, check for corrosion on any of the connections. You could also run a temporary clean power supply and see how the pump behaves.