"If I close the raw water sea cock the water stays in the bowl."
Very strange! Archie mentioned the seal between the intake pump and the discharge pump. Sounds like a good place to start.
Here is a link to the parts list. The seal Archie is talking about is #19 on the drawing.
A bad joker valve could let it leak out the discharge hose but closing the intake seacock wouldn't affect that.
A complete motor and pump assembly for that toilet runs about $195.
You can also convert it into a Raritan Sea Era for about $425. The Sea Era is quieter and there is no connection between the intake and discharge pumps.
You should contact Jabsco customer service. They are nice folks and I suspect replacing the seal will solve the problem.