Well if I were you, I'd get the original head
in good condition again, and leave it plumbed outside directly to the sea. That way when you are traveling, you can use it and not be putting anything in the boat.
You can even use it at a dock
for just peeing. I know I don't have a problem peeing in the sea, but #2 is another story. Use your other head
with the 40 gallon tank to take care of that.
It's a nice option to have, a direct deposit head and one with a holding tank
. That way you've got it covered and you are legal
. That way you don't stress you tank when you don't have to.
The plus side is that you put all that money
right back in your pocket and you are already set up to hit the sea.
Best of luck.