Ahoy All! I've a Hunter 27, 2006 (your little brother), however the 1 1/2 discharge hose from the Jabsco head and through a bulkhead to the discharge tank is quite similar to yours. I just purchased this boat and I knew there was some liquid seepage from the hoses somewhere so I used it as a bargaining point. I wish I knew how it was originally plumbed for the waste side. The waste hose from the holding tank comes through a bulkhead and I believe it to be original. From the discharge at the toilet to the bulkhead was at least 5 or 6 junctions, (hose, boot, elbow, boot, shutoff, boot) The boots did not fit snugly on the 1 1/2 odor fighting waste hose, thus the leaks. I replaced with one new hose all the way to the bulkhead with a one way flapper valve at that junction. Seems to be water tight, I haven't tried to pass anything but liquid through the flapper valve, I'm a little concerned.
My question is, "Does anyone know what the original plumbing configuration was, does it need a one way valve?" My holding tank is above the toilet and has an overhead loop with a vent of some sort.
Thanks, Martin in Tulsa