Check the Through Hull Fitting - From Inside.
Dan: Recently I replaced all hoses and the holding tank on my 1989 33.5. Following our beloved Peggy's advice, I replaced the small vent hose with a 1" variety. When I removed the old vent through hull, I found it clogged with a spongy material. It looked as though the hull liner had been installed after the hole was drilled for the vent fitting, then the fitting was just shoved through the liner and screwed on to the interior elbow. In the process the foam portion of the hull liner was left in the vent fitting. Having owned the boat for 10 years, I had on several occasions backwashed the vent line with water from a hose. Little did I know that most of the water was squirting right back at me. The foam was black with discoloration. Enough air may have passed through to allow the pump out to function, but I have had more than one marina owner tell me that he suspected a problem with my vent line. Rather than removing the hose from the tank, I would suggest removing the hose from the through hull fitting elbow, then unscrewing the elbow fitting from the through hull, and checking the vent fitting from the inside. With the vent hose off from that end, it should be easy to back flush some water through it into your tank (with the shower hose?), as well. Best of luck. Ron Captainronb@earthlink.net
