pinchio welcome aboard
are you sure the locker drains into the engine compartment and not to a side thru hull fitting? Have you tried using a hose to see if any water is making it through?
Not sure what you have tried using to open the blockage but an electricans fish tape may help as it is somewhat flexable to make bends.
1997 2400 SCR
5.7 Vortec / Bravo 2