Our 1991 P42 still has the original forward and aft cabin Jabsco electric macerator toilets. They still work, but recently I decided to tear into the aft unit to see whether a pump symptom was due to a failed part/parts. The PO had replaced both pumps some years before and both original units were still on board as spares. One had frozen up, but the other still worked. During the process I learned a few things.

1. These toilets have a flapper valve, not a joker valve. If you order a joker valve for your original toilet it will not fit.
2. Replacement parts for the old units are no longer available.
3. They do have an upgrade kit whereby a new motor and macerator along with a joker valve fits to the old bowl.
4. The old motor and macerator assembly is very robust and simple. If it still works keep it.

Our original system still remains in good working order. They do make considerable noise during the flushing cycle, albeit a brief one at that. Just make sure that you only flush toilet paper and body waste. It really does not like trying to chew up these new fangled wet wipes. Even the flushable ones. That is another story.