Open bow drain?

[SS MAYFLOAT]

89 Rienell 190 open bow. The water will not drain from the compartment. I removed the panel exposing the drain line. I found a back check valve that is severly clogged. It is made of molded plastic and cannot be taken apart to clean. I let it stand in CLR for 2 days with no success. I can't get water or air to pass through it.<br /><br />I have checked with the mega mall with no luck on finding the critter. When there is nobody sitting in the bow, the outlet is above the water line and when it is full of several people, the outlet is then below the water line. So it needs to have this check valve in there. My problem is where do I find one? Any suggestions? Thanks.....