Open the seacock
If the macerator runs, but isn't pulling any waste out of the tank, the thru-hull is prob'ly closed. If waste is also backing up into the toilet, there's a good chance that the tank vents are blocked, which also prevent any waste from being pumped out or dumped. So the first step is: make sure the vents are open before trying to either one again. Why haven't you just gone to a pumpout if your tanks are full and you can't figure out how to dump 'em?My next question is, WHERE have you tried to dump the tanks? 'Cuz it's illegal to dump a tank within 3 miles of the nearest point on the whole US coastline...which means, if you've tried to dump 'em in the bay, you've been trying to dump 'em illegally. And that can cost you BIG bucks in fines if you're caught. I suggest you check out the link below.