-
Not familiar with the marathon system, but sounds similar to the Headhunter system. I could not get my Headhunter system to maintain a constant level until I replaced the plastic pipe inside the tank. The original plastic pipe had become brittle over the years and had hair line cracks in it that allowed air to leak out. It was not an easy job to do, there was very little room to work. One of the pipes broke in the few places because it was so brittle. Thankfully the pieces were small enough that they flushed out when I dumped the tanks.
Chuck
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL