Need help from 330 & Marlin owners with vacuflush issue

I just found there is a wealth of "how to" videos on YouTube. Some of the guys are pretty informative and give probable causes for certain symptoms. Search "vacuflush head repair". Lots of things you didn't know that you didn't know you didn't know. Ya know??? Ball valves and seals, duckbill valves, vacuum swicthes and pumps - bowl to tank.

I should have known. A few years ago, my washing machine's agitator stopped turning. I searched YouTube using the brand, model and symptom. Up comes a video showing what was broken, the part number and how to replace it. Less than ten dollars for the part and it was done in 20 minutes.

Thank you Dennis (and Jim).

I agree, I'm thinking I have a clog and like your idea of snaking my way to and from the Vac. Tank.
And yes, I pump out 3+ miles out. My boat is in a harbor on the ocean and I'm out in blue water fishing all the time - blue water that is until I empty my holding tank!

Thanks again for the tips and link above. This thread should benefit many now and in the future.

News Update on my "weak" vacuflush issue.

After essentially pulling everything apart, I learned:
1. No blockage between the bowl and the Vacuum Tank
2. No blockage between the vacuum tank and holding tank
3. One duck bill looked really good, another was slightly off it's seat (not inverted).
4. My Vent line was plugged.

So, after clearing the vent line, everything worked better.
I think the clogged vent line created a vacuum somewhere which disallowed the Vacuum Tank to achieve full pressure.

After replacing both duckbills and cleaning everything, it all works great now.
I did notice I get more pressure (or suction) in the bowl if it is only 1/3rd full of water.
More water = less pressure. Less water = more pressure.

There you have it. Hope this helps in case you ever tear into your system.