The engine installed MIGHT be one that does a large return to the tank , to cool & lubricate the injectors.
If a cheap tank selection valve (return not switched ) was installed the balance line will be required, to maintain vessel trim underway.
IF you can get it operating, the line , with a few fittings will work as a low point grunge drain.
Just beware of the Sheen Police, and donate the fuel to the folks wanting to burn old lube oil. It will be far less harmfull for their engines.
-- Edited by FF at 05:10, 2008-02-02