Don't be too quick to replace it
Low voltage is most common cause of sluggish discharge from electric toilet. So there are several possibilities: 1. your battery is getting old...2. not enough battery power to handle the toilet in addition to all the other 12v stuff you're running. Which means you either need another bettery or you don't run your engine enough to keep it charged...3. the toilet isn't on its own separate dedicated circuit, shared by nothing else that can pull power away from it. Put a volt meter on it and check it...if it shows the toilet is getting less than a full 12v WHILE FLUSHING, that's the cause of your problem. If low voltage--which btw, can also damage the toilet motor--isn't the problem, check your discharge line for sea water mineral buildup that has reduced the diameter enough to restrict flow. Or your tank vent may be blocked or partially blocked, creating backpressure that you're mistaking for a clog. Or, if the toilet is actually clogging, you aren't flushing long enough to clear solids and TP from the line...a problem you'll also have with a manual toilet. As for the 1" discharge line, that's not your problem, but it's easy to fix: replace the discharge fitting with a 1.5" fitting and the head discharge hose with 1.5" hose. If you're still determined to replace the toilet with a manual, go with a Raritan PH II, not a Jabsco. Do NOT remove any vented loops...vented loops are siphon breaks that have nothing to do with your flushing problem. What is the make/model of your current toilet?
