Bilge pump sucking air?

ahpeterson · Posted: Mon Feb 04, 2008 2:18 pm Post subject: Bilge pump sucking air?

Hi all,

I just picked up my C-Dory, and one thing I noticed when washing down the boat was that the pump was sucking air for a long time before it got ahold and started pumping. I noticed there was a good amount of crud in the bilge, so I cleaned it out and tried again, and the same thing happened. It was going for so long (several minutes) that I went and took it out and put it on its side in the water, which seemed to get it going.

Subsequently when I filled the bilge it did OK, but I'm curious if this is a known issue with these pumps?

lloyds · Posted: Mon Feb 04, 2008 3:04 pm Post subject:

Mine does the same thing, maddening. I don't know for sure, but I don't think there is a backflow preventer upstream from the pump. Don't know if that would help or not. Something else I thought of trying was getting another pump, without the automatic feature and adding a strainer attachment that sits closer to the bilge floor so it could start pumping without waiting for a head to build. In mine the water has to be about 2 inches deep to really start pumping right away. I have opened and cleaned the strainer repeatedly. That is not the problem.

ahpeterson · Posted: Mon Feb 04, 2008 3:08 pm Post subject:

So does your pump just spin forever with no air or does it eventually grab on? My primary concerns are the pump burning out and the battery getting drained.

lloyds · Posted: Mon Feb 04, 2008 3:11 pm Post subject:

Mine just spins free till it grabs on. Most of the modern pumps can run dry for pretty long periods. I had one once that ran overnight in the driveway because I didn't pay attention and turn it off after cleaning. It was fine after that. At least I can say something good about them.

Notayot · Posted: Mon Feb 04, 2008 9:22 pm Post subject:

As far as I can tell, there is no backflow preventer in the outlet line, and no foot valve in the pump. Mine (both) are the automatic Rule pumps with an internal float switch and stainer. When I try to test them with an inch or so of water in the bilge, they suck air and pulsate as they grab water. On the other hand I had been out for 2 or 3 days and had collected a couple of inches or rain water in the cockpit under the floorboards. While towing the boat home, as I rounded a slight corner to the left at 35 MPH the rear pump came on and sprayed across the curb and the sidewalk with a horizontal stream of water about 4 feet off the ground. The spray lasted 20 seconds or so and looked like a fire hose shooting horizontally. No one was walking on the sidewalk, thankfully. I assume that the pumps will do their job when and if asked, but I still test them several times a year.