Ballast Pump Problem - Centurion

I have a 2003 Centurion Cyclone with 3 stock hard tanks. It uses 3 Mayfair Cartridge style pumps. These are the yellow ones with the black tops.
When I try to fill the tanks the pumps turn but do not flow any water. If I crack the top of the pump open they spill water out of the top and when the top is snapped back on they pump fine. Emptying the tanks works fine. Any ideas what may be up with these?? Thanks -Bob

They are getting air locked. I believe the intakes are under the platform in 2003. Try backing the boat up to force water in. Others have said that the engine must be off because the exhaust puts air into the pump intake. I never had that problem with my 2004 with that same configuration.

What he said

My rear port side pump sometimes is air locked at start up. If I reach down and lift and/or jiggle the intake hose a bit, it will then "load" with water and begin pumping. I normally fill my fat sacs with the engine off. Interestingly, with the engine running, the starboard side picks up too much air from the exhaust, while the port side doesn't. Since it would take the starboard side longer to fill with the air getting in, I turn the engine off while filling.

I agree with Patrick. The exhaust ports are near the fill ports on my Lightning. I never fill with the engine on. Like Patrick it took a knock to get one of them going this last season. I did replace the cartridge on one pump thus year.

Cartridges are pretty cheap and very easy to replace.

Agree with all. What I used to do was slam the boat in reverse turn off ignition and flip the switch. Never a problem unless I was on a river with a strong current. In that case I reversed the boat into the current and then did the same. It's a pretty common problem with these pumps due to their location, so don't worry too much. Also try cleaning the rubber seal around the top and put some vasaline on it SMALL AMOUNT to seal it a little better.

WOW thanks for all the quick responses. I tried the "slam it in reverse" method this afternoon and got 2 of the 3 pumps to prime. I will lube the seals tonight and see if that helps. Anyone have more of a permanent solution besides the jiggle, knock, and slam methods? (sorry yankees but the lake was 82 today and f-l-a-t).

Assuming your impeller is starting up and spinning normally when switched on (if not you need a new impeller) I agree that it sounds like an airbound impeller. Also assume you know not to fill it while idling/engine running.
Last tip is to unscrew the screen "mushrooms" under the swim platform and make sure there is no debris/obstruction in the pump inlet.