Just spoke to a friend of mine. He suggested mounting the vent on the transom at the back of the boat so that odors are minimised. They won't travel over the boat into the cockpit.
Now, the head is located on the starboard side, pretty much forward in the boat. So we are talking a hose length of about 20 feet...
Through the cabin.
I would probably have to keep the hose very high, cause if I go low near the floor then finish up high on the transom, if I get some liquid in the dip, it will block odors exiting.
If I get liquid traped in the hose maybe it would act like one of those beer fermenting valves. I could sleep at night and listen to the occasional bubble when the holding tank
generates a new methane bubble (fart).
Then what if I heel and a turd gets in the hose? Constipation.
This is sounding really stupid.
I have talked myself out of this idea already.
The only reason I am going to post this is so you can get a laugh.