Run Engines at 4000-5000 for 20 Seconds to Flush???

[Dean P]

Checking out the Service Manual and noticed this flushing procedure. It states 4000-5000 rpm for 20 seconds. Does anybody do it this way? I know there's been a lot of talk about it but was surprised to see this. Is this right?

 

[JetTech72]

I normally start the water about 5 seconds before starting the engine. After letting the engine run @ idle for about 1 minutes with water flowing, I close the water & do a couple throttle blip to evacuate the excess of water in the exhaust system.

 

[Dean P]

It's not a good practice to start the engines with the water already running. This is frowned on by many. Start engine, turn water on, wait x-seconds, turn water off, turn engine off. This follows what is stated in my pictures above and by many jetboater members.

I'm curious as to why the manual states to rev the engine at high rpms for 20 seconds as a flushing procedure.