Porta potties are the easiest solution on smaller boats as they require no plumbing and can be emptied easily in a regular shore side toilet. Second is a Jabsco manual flush toilet. Requires: raw water intake and through hull valve, holding tank, and either a manual or electric pump out to the ocean with a valve when operating beyond 3nm of land. you dont need the manual pump out as long as you have a deck connection to suck the tank out at marinas but they are nice to have.
Thanks for all replies. Had the porta potty west marine brand and the big plastic nut between the tanks cracked. They want 35 for the repair kit to remedy the problem but not address the design flaw. Ive got plenty of buckets to have a multiple head boat however the boat is plumbed with through hulls for waist pickup and pump out so I would like to put a nice one in that a wife and a guest may feel a bit more comfy with. Many selections on line as well as west marine.
They clog so easily and you have to keep paper out that it becomes uncomfortable for non boaters IMHO. I would try a bucket with a seat and waste bags from the camping store or a diy composter. Cover the waste with shavings. But make sure your buckwt is held securely.
Top of the line is a vacuflush system, but not sure if that works for a 20 foot boat. That said a jabsco system, either manual pump or 12v/macerator set up works fine. A bucket and sawdust? Are you kidding me. Need to make sure you have enough room for decent size holding tank.
I don't think you'll get a vacuflush on there and it's overkill. My 20' skippy had a thru hull for a head but it did not meet current regulations. I'm pretty sure you need to install some holding tank and y-valve to be legal. You can buy a small holding tank direct from raritan for pretty cheap. They have MANY prefab sizes you can choose from. The standard west marine electric flush head will serve your purposes nicely I think. All said and done I think you'll be looking at about $650 in parts. It would be a nice addition though and make your wife and guests much more comfortable. Good luck.