From Carolyn @ GW
Here’s the basic hull stringer/ pvc layout for the 268 Islander. The arrow shows a long 1 ¼” pvc drain pipe that runs under the fuel tank compartment and drains the forward bilge area to the aft bilge on this boat. The 2nd small piece of PVC that is circled is the fuel tank compartment drain tube. Both tubes run in the bottom of the keel on our boats. To drain the fuel tank area we recommend elevating the bow up so that the water will drain out the aft of the boat.
I have a few more question back out to Carolyn at GW....
How does the water get out of the forward fuel tank? Are there two drain tubes, one for each fuel compartment, that run to the aft bilge?
Should the fuel compartment drains always be open or should they be plugged after draining? Seems to me you would not want a leaking fuel tank to drain into the bilge!
Edit: Added a image of my aft bilge. It looks like a 1 1/4" PVC pipe that Carolyn said should be from the forward bilge. Also it looks like a smaller PVC pipe to the aft fuel compartment. I have a endoscope type of camera about 6' long that I will snake the 1 1/4" tube and see if I can get thru to the forward bilge. Stay tuned...
Edit: Added photo of the forward bilge under the shelf for the shower sump. In the center of the photo you can see the 1 1/4" PVC tubing coming thru. I tried to snake the tube aft to forward but it seemed to turn about 6 feet in. I did put some pink antifreeze in the aft bilge and lowered the bow of the boat on the trailer. Pink water did flow forward. Apparently my boat was pretty level and both bilges had water. I blocked the trailer jack 4 1/2" and put the bow back up. I tried to snake it back forward to aft but could not get the snake started. My endoscope camera is now in the garbage can.
Also the little hose coming out next to the 1 1/4" in the first picture is actually a reinforced vinyl hose with at plug in it. This would make sense because it is the fuel compartment drain. In my case, if I washed the fuel tanks I would have to pull the plug to drain the compartment. This matches what I found when inspecting my tanks. I had to vacuum the water out of the compartment.