I know I can run my 470 without the outdrive by supplying water with some pressure by a couple of different methods. I'm trying to find if the noise I have been hearing is from the outdrive or the engine. From what I have been observing I will need to run it about 1 to 2 minutes. Is this just matter of cooling the engine, or is the water needed in that short of time to keep the exhaust gases from being too hot for the exhaust plumbing? Thanks.