If the sea water version, install a vented loop in the intake line. 'Twould be best if you can put it between the pump/motor assembly and the bowl...if not, between the intake thru-hull and the pump/motor assembly. It needs to be at least 6-8" above waterline AT MAX HEEL, which on most sailboats puts it 2-3 FEET above the bowl.
This will prevent water from rising in the bowl as sea water OUTside the boat seeks its own level INside the boat via the toilet bowl when the intake thru-hull is open..and will save you from yourself if you forget to close it when you leave the boat.
If you have the fresh water version, give Raritan tech support a call Monday morning.
800-352-5630
--Peggie