You shouldn't be getting any water into the bilge from the thru-hulls unless there is a leak in the hose or the couplings. If you take those deck drain plates (the ones with the holes) out, and have a small enough hand, you can access the hoses that go to the thru-hulls. But water should go from the deck, into the drains, through the hoses, and out through the thru-hulls -- again there shouldn't be any water coming into the boat/bilge via that route unless it's a small amount in the hoses - if the thru-hulls are normally under water. Incidently, in what is probably the worst design flaw I've seen in my Aquasport, those drain hoses bend almost immediately at a 90 degree angle, effectively "kinking" and reducing the water flow by at least least 50% of what a "straight hose" could attain.Bill'88 222 XF