After finding myself out cruising with a full holding tank and no pump out, I've decided to add a macerator pump so I can pump out myself.
That's fine as long as you understand that you can only use it in open sea at least 3 miles from the nearest point in the whole US coastline. (If you're not in the US, refer to the legla requirements for the country you're in).
Can I use a macerator to empty the bowl through the flapper and joker valves?
You can't use the same macerator pump to empty both the toilet and the tank, so you'd need a second macerator. You'd also have to remove the toilet pump, which means you'd no longer have any way to bring flush water
in, and also because the macerator pump and the manual pump won't move bowl contents at anywhere near the same rate...so you'd be constantly "frying" impellers in the macerator and or creating backups in the discharge line. Bottom line: it's a bad idea, but if it any consolation, you're not the first person to think of it.
If you want a macerating electric
toilet, replace the manual pump with a real macerating electric toilet. Most toilet mfrs offer "conversion" that replace everything south of the bowl, reducing the price
considerably...only about twice the price
of a macerator pump. Any bowl that mounts using a 4-bolt + pattern will fit any of the "conversions." IMO the Raritan
SeaEra SeaEra Conversion Kit
is the best choice, but the only one I'd advise you to avoid is the Jabsco
29200, which only replaces the manual pump with what even Jabsco
admits is a very poor excuse for an electric toilet.
it according to mfr's specs is critical to trouble free operation. So the right wire size for the distance to the battery
(which is always the round trip distance) is essential...as is the need to have enough power for the toilet. All electric toilets--even including your bad idea of installing a macerator pump inline--need to be on their own separate dedicated circuit, shared by nothing else that can pull power away from it 'cuz low voltage will quickly destroy any electric motor
BTW, the toilet is well below the waterline and gravity fills
That's NOT how it or ANY toilet should be installed...in fact, it's a good way to sink a boat! Read the installation
instructions for your toilet and install it correctly. If you don't have the instructions, you can get them from the mfr's website. I'll send you the link if you'll tell me the make/model.