My last boat was 25 years old when I bought it. The head was an illegal and smelly mess. Tore out everything and installed a full size portapotti MSD with deck pumpout. No more smells.
I was left with extra thruhulls and experimented with a urinal tube to greatly extend time between pumpouts. The 5 gallon capacity of the portapotti encouraged this thinking. I found the direct overboard drain very convenient and want to equip my next boat with a urinal.
In the summer of 2010 I had a routine boarding by the Coast Guard at Friday Harbor in the San Juans. They gave my boat an inspection and found no infractions. I have the receipt to prove it. There were no particular questions about my sanitation installation.
I think this post could result in some interesting positive and negative input and some nuggets of wisdom as well. Mostly male responses I reckon.
First of all, it must be understood that urine is not sewage. Sewage is defined as solids suspended in water. Urine from healthy people is sterile and harmless to the marine environment. That being said, I imagine regional law enforcement could have various definitions of sewage, perhaps requiring urine to be controlled as graywater.
There is at least one supplier of a compact porcelain wall urinal with plumbed flushing valve. This could make for a tasteful installation but I wonder how it could be drained by gravity only, while using a thruhull safely above the boat's waterline.
I have used a 3/4 inch tube with a funnel clamped on the inboard end. Kept a 1/2 gallon jug with a weak vinegar/water solution nearby to provide a flush of the line after each use. Never had any odors this way, never had to risk the public display of a man pissing over the side of the boat, never risked my life falling overboard with my fly unzipped.