Waste Tank Issues
 

I have another Gremlin in my boat this year.

When I pump out I can only suck about 2-3 gallons out. I thought that maybe my vent was plugged but I took it off and blew air through it and everything was clear. When we're pumping out you can hear the vacuum pulling through the vent in the side of the boat.

We figured this out because when it was done pumping I wanted to flush out the tank with fresh water and a few seconds after putting water in the tank was overflowing again.

Has anyone else had this issure? Does anyone know if the hose that does to the top of the boat goes in the bottom or top of the tank. The thought right now is that the hose inside the tank has come off and is not allowing me to suck off the bottom which is why I'm only getting the first couple gallons out off the top. I'm lost with ideas and its a real pain not being able to use the bathroom more than twice before having to get pumped it.

I think this is going to be a real chitty job.

Normally, on a waste tank there is a low exit fitting and a top entry fitting. The head toilet should be plumbed to the top entry fitting on the tank and the top deck pump out fitting should be plumbed to the lower exit fitting on the tank. What model boat do you have? You should be able to visibly view the tank as it's normally right under the pump out deck fitting and then track the hoses.

If I had to guess, you might have a kink in the hose going to the deck pump out fitting which is causing the flushing with fresh water to back up quickly.
Or the hose doesn't have enough downward angle to keep up with the amount of fresh water flushing your trying to feed down it. This is a common issue with bass boats and their fuel fills.

I have a 358. I can only see the lines where they connect to the deck fitting and then they run under the floor. I don't believe you could actually kink these hoses, they are a harder plastic, I don't even think you could compress them with your hand. I think I found a small access panel in back of the A/C Unit in the bathroom to where I could at least see the the tank (maybe?). I hate to take out the bolsters and floor panel but maybe we'll have to.