I have owned this boat for 4 years and the toilets have been trouble free. This weekend, the vacuum pump would kick on and pump every 10 to 12 minutes. I located the unit, and saw the previous owned had a supply of duck bills. I removed the inlet to the pump from the tank, and the duck bill was deformed open a bit. It is the “S” pump, so it had only 1 net valve and 1 outlet. I then removed the outlet valve, same thing. Replaced and reassembled. Hooked up, and she was still cycling too often. I opened the access panel and saw a pin hole at the top of the output hose, that was sucking in air. For now, I taped with electrical tape many times, and then reclamped it. Test A OK! So, take the diagnosis a bit further, as you may have a pinhole in the hose too.

I have to say it was not as bad a job as I thought.