My 1986 20' Pro Line has developed a bad case of blockage in the fuel tank. I can blow out the fuel line, but it just comes back in a while. The tank is a bit rusty, and I cannot tell if the attachment on the top of the tank to which the fuel line from the engine is attached would screw out, or if it is permanent. If it screws out, I would like to take it out and clean it good, but hesitate to force it if it is not supposed to unscrew. So, the question is, does anyone know whether or not it unscrews? Original tank.