If you're on a tight budget this year, just replacing the motor on the Jabsco will solve your immediate problem. But if your boat budget can stand $700, the Raritan Marine Elegance is is the top rated electric macerating toilet. (The Raritan SeaEra is also an excellent choice, but there's not enogh difference in the price of the "QC" fresh water version and th Elegance to go with it IMO) Not only is the Elegance the quietest marine toilet, but that price includes the optional "SmartFlush" panel that provides 4 flush choices: bring in water ahead of use (essential before solids), dry flush, low water flush and "full" flush for when you need it...all of which conserves fresh water and holding tank capacity.
Raritan Marine_Elegance Promo.pdf It's designed to use pressurized fresh water but if there's a little more $$ in your budget, adding the "sea/fresh" option
Raritan seafresh.pdf allows switching between fresh water and sea water at will, doing even more to conserve fresh water.
Give Hopkins Carter Marine a call:
Hopkins Carter Marine Raritan Marine Elegance
--Peggie