remove them from the hull, soak in water / simple green (degreaser) and some rags / hose. just make sure all the tiny holes are clear.
yip that's pretty much all I do, i have a small electrical tester with a fine point and stick it thru every hole and then blow it with air, some water, then air again, they get really nasty inside.... just keep rinsing until they stop pushing out nasty water, and then you'll have 80% of it, but they are very easy to remove and put back, and lately, i've been using some bilge cleaner and throwing it down in the hull, it does seem to help and the water swishes it around, but on many ski's the scuppers get really nasty since they kind of lay there in where all the gunk collects.
I considered throwing mine in the dishwasher but I figured my wife would kill me if they sprayed gunk all over the inside of the appliance
ps.. while they are out... spray some purple power and rinse out the inside of the hull with a pressure washer (don't soak the carbs/air cleaner, just the hull) clean that area really really well, sometimes it takes two or three attempts to get the layers of crud off, they will be less prone to clogging if you start out with a clean hull.
it helps if you have a wet vac and then you can spray, suck, spray suck and after about a half hour of doing that, you'll be sucking up nice clean water. its a bit more of a pain (well, actually its a big pain) relying on the drain plugs to rinse out the gunk, the wet vac helps a LOT !
even with a relatively clean ski, you will be amazed at the gunk that comes out, and make sure you rinse as much as you can, since it gets really nasty under the engine and fuel tank. I considered my ski to be fairly clean and when i pulled my engine it was absolutely disgusting down there !
get it all clean and you won't have that a$$ smell when you take your seat off.
