So i have noticed i can hit my manual bilge pump from time to time and about a half a gallon of water will come out the rear pumpout, this has been going on for the last couple of times out, my valve is on recirculate when i launch and i back in nice and slow, so when i got home today i started checking things out and found the drain plug o-ring is broken but still in tact it was hard from weather beaten, so i disassembled the red plug end it has 2 small phillips screws you loosen and it comes off the wire its clamped too. i obtained a new o-ring out of my service truck for work and replaced it, this might also be caused from being inserted in and out over time in dirty or silted water so if your experiencing the water problem you might check this item and clean it now and then to prevent wearing prematurely, hope this helps i have a z521c