Re: macerator pump not dumping.... suggestions?
Could be a couple of issues. First, if you are dumping thru the macerator, please tell me you are >3 miles from any shoreline (it's the law).
There should be a ballcock valve at the brass thru-hull valve. Is it open?
More than likely, there is a blockage between the tank and the macerator. If the tank hasn't been pumped out in a while, toilet paper and... *ahem* ...stuff can solidify and easily block the pipe between the tank and the macerator. The only ways to fix a clog in the pipe is:
1) Go overboard with a garden hose. Open the seacock and back flush water thru the discharge port. Don't run the macerator, you just want to try to stir everything up a bit

eek

. Then try the macerator again.
2) Pump out at a fuel station, flow ample fresh water back into the tank thru the waste pumpout port, run the macerator and discharge the fresh water. Repeat.
If using an onboard head, it's always best to empty the holding tank at the end of the day/weekend. Also make sure you use nothing but marine toilet paper. It will break down to nothing when in contact with water whereas regular toilet paper becomes giant wads of paper mach?.