Removal of thru-hull transducer

[Basketcase]

Hey guys. In my 20' sceptre, there is a rather large thru hull transducer that has long since been abandoned. I'd like to remove it. What should I do with the hole? I've got what I would need to fiberglass the hole, but I just dont want to do the work. What I would like to do would be to use the hole for a pickup for a wash down pump. That would be great. My only concern is that I dont have access to it without removing the fuel tank. I really think this thing must have been installed before the fuel tank went in, as it is not something I can reach through the pie plate in the splash well. The only reason I can think of not to do this, is that I won't have good access to a seacock. I don't think I could reach it if I needed to. Is there a solution to that? Any other ideas?