ITT Jabsco Macerator Pump Heavy Duty 12V - 18590-2092ITT Jabsco Macerator Pump Heavy Duty 12V The 18590 models are also ideal for emptying fish boxes and livewell receptacles. Very often the livewell tank will be above the waterline of the boat. When this is the case, gravity can be used to empty the livewell tank. If the livewell tank is not installed above the waterline it is beneficial to use Marine Macerator Waste Pumps for evacuation due to their self priming capabilities and grinding properties.