[C320-list] Accessing holding tank vent

[Dave Hupe]

I just did an extensive job of replacing all of my waste tank sanitary hoses, the intake water lines and thruhull/valve feeding the toilet , and replacing the tank vent hose.  My boat is 1994, so this may not be the same for you.
The medicine cabinet removal was very easy.....just remove the screws around the cabinet perimeter and pull the cabinet straight out.  Access to the higher cutout is much more difficult.  It required removing the cover panel that is above the shelf over the medicine cabinet.  To do this, I first had to remove the teak shelf strips, remove the teak wiring cover behind the fluorescent light, and remove the mount screws of the light fixture (first must remove the frosted lens cover, bulb and shield behind the bulb) so it can be shifted out of the way.  Next, remove the electric outlet cover, disconnect all wires from the outlet (tape/mark the wires where they mount for reference), then completely remove the outlet.  
Lastly, remove the screws from the back cover panel itself and try to pry it gradually out/off.  As you do this, feed the wires back into the hole in the wiring outlet box.  My panel was very difficult to remove because I believe the plywood of the panel was slightly swelled from past moisture problems.  Once removed, I wound up removing the perimeter rubber trim on the panel (just stapled), trimming 1/4 inch off each of the wood ends of this panel, then reinstalling the rubber trim before reinstalling the panel.....much easier to put back on than take off!
The black plastic tank vent thruhull fitting has a nut on the inside, available through the upper cutout that you could probably tighten (although access will be tough).  Getting your vent tight will be done by tightening either the inside nut and/or tightening the outside cover of the vent. 
Hope this helps.
Dave Hupe
1994 Cat 320 (hull #32)
Holland, MI