I don't think you need a new macerator...
If the motor runs, but doesn't pull anything out, it prob'ly just needs a new impeller...in fact, it should be replaced every couple of years at least as preventive maintenance.Manual for the macerator, which includes instructions for replacing the impeller, is on the Jabsco site here: http://www.jabsco.com/files/18590_series_sealed_macerator.pdfThe other possibility is a blocked tank vent, causing the pump (also a pumpout) to pull a vacuum that would prevent anything from being pulled out of the tank. You might want to check out the link below...it'll take you to a comprehensive "marine sanitation systems 101" manual.