What toilet do you have now?
Depending on the make/model/age of your current toilet, it may be time to decide between rebuilding or replacing...but neither will solve your backflow problem. So let's talk about that first...then we'll get to electric toilets.If the toilet is pumping smoothly--if backflow seepage is your only problem--it prob'ly doesn't need rebuilding...in fact, depending on what's causing it, rebuilding may not cure it longer than it takes a new joker valve to get a little wear.Backflow can only occur if there's anything in left the head discharge line after you stop pumping TO run back toward the toilet. It doesn't go through the pump, it's pretty much a straight shot back into the bowl...so rebuilding the pump won't cure it. Backflow can be caused by any of several things: 1. (the most common) is not flushing long enough in the dry mode to move bowl contents all the way to the tank--or at least over the top of a vented loop or any other "hill" in the line...2. a partially blocked tank vent creating backpressure in the system...3. sea water mineral buildup in the hose that's reduced the diameter, also creating backpressure. All of the above are problems downstread of the toilet, not in it. The joker valve in the head discharge fitting will slow it down, but it's only supposed to prevent a sudden flood...it's not supposed to totally block slow seepage. A brand new one will, but only till enough flushes have gone through it (a couple dozen) to keep the "lips" from sealing tight again. Joker valves should be replaced at least every other year...cost: about $12.Now to whether it makes sense to rebuild or replace. If it's been more than about 5 years since the last rebuild, it's time to do one or the other...the only questions are: 1. Is your current toilet worth the cost of a rebuild kit...and/or whether it is or not, you'd just rather the "push button convenience" of electric instead. If that's the case, a boat the size of yours should certainly have the power resources to handle an electric toilet...and the Raritan SeaEra is the best "bang for the buck." It's available as either a complete toilet or a conversion...both the complete toilet and the conversion are available in both sea water and pressurized fresh water versions. Check it out on the Raritan site at http://www.raritaneng.com I'll be glad to answer any questions that aren't answered there.