A water hose, applied from the back
end to flush it down into the bilge. Or an electrician's "fish tape" which is often under $10 and very handy on a boat, used like a plumber's router. Or for the matter, look for a small plumber's router. Don't get too aggressive because if you chew through that hose--yeah, oops.
If the clog is something like old paper that has hardened up into a plug
, it is possible that it will get soggy enough to dislodge if you let it soak again for a while.
Meantime, you want to order a strum box to put over the end in the bilge, to keep crud out of the hose after you clean it out or replace it.