I have same problem like Gripit. Sometimes it is to late to do a correct flush. My neighbors cant stand it when I do it at Noon. I can only imagine what they would do at Midnight.

What if you where to flush the engine some place past the thermostat? My last boat was a jet drive with no thermostat and I use to flush it all the time without the engine running. I really did'nt know if I was accomplishing anything because the boat got stolen before any corrosion could be notice.

Has anyone heard of Guardian Engine flush system? You hook a hose up to it and it is supposed to flush the block and risers without running the engine. Comes with hoses and injectors, the hoses attach at several points ion the engine, injectors are supposed to create a pulsating action. I installed a couple of years back, and I guess it works.

Check out this article and the website -- http://www.boatfix.com/mst/why.asp -- I had one on a CorrectCraft inboard. It seemed to work exactly as advertised. Could also be used for winterizing with an attachment.

If you flush with this system you DO NOT run engine while using the Guardian. You can install an auxiliary flush sytem inaddition of you wnat to run engine.