Originally Posted by sparkey
It works ok but you must not start your engine with this system in use.
This injects the water into the cooling system above the impellor so thete is no water around the impellor and will burn out .
I sort of dispute that statement (though I agree one should follow the manual, and not run the motor on the flush attachment.) Running off a powerhead-mounted flush inlet, the water runs backwards down the pumped water line, so it does, in fact, rinse out the impeller and housing. This can be verified by seeing how much water comes out of the intake screens. With the top mounted flush adaptor running the motor causes the impeller to try and pump the draining water back up, and that's where you run into problems (maybe.) I have heard of several people who routinely run the motor on the flush attachment, and have yet to hear of any horror stories (though I'm not going to be the first, either.)
Units with the lower unit flush adaptors (i.e. a threaded insert that goes into a plugged port on the leg, that you connect a hose to; a la Suzuki) may or may not be run, depending on the manufacturer. Suzuki says it's OK; Honda (as far as I know) says you can't.
Short version: Do what the manufacturer suggests in the owners manual, and you shouldn't have any problems.