clogged scuppers

[CurrentObsession]

Power washed my new to me 2001 Stingray CC today and the forward storage boxes filled with water even though they have corner scuppers that drain with hoses thru the side of the boat just above the water line. I tried to push thru what I assumed is a clog with some extra 14-2 electrical wire but didn't get very far. I am worried about breaking something. Do these systems have a check valve somewhere? Any suggestions on the best way to get them unclogged? Out side fitting does not have a flapper.

​Thanks

 

[Bondo]

Ayuh,.... I clean the hatch drains on my houseboat with a blast of compressed air,....

Once clear, a blast with the garden hose occasionally keeps 'em clear,....