The Jabsco 37010 is a sea water toilet that has two impellers--one that pulls in flush water and one that pulls waste --or water--out of the bowl. It has an "integral" pump that does both simultaneously....which means it's not designed to bring water into the bowl and hold it unless you install an optional 3-way flush rocker switch (water in only, flush only, water in and flush out simultaneously).
But there can be another problem if you keep the inlet thru-hull closed and ONLY add water to the bowl: without water going through it, dry friction heat "fries" the intake impeller.
You won't have to go through WM to access the 37010 owners manual directly from the Jabsco site
Jabsco 37010 owners manual
--Peggie