2001-2005 Yamaha WaveRunner GP800R Factory Service Manual, Page 329Get this manual
E 1Put the watercraft on land in horizontal position2Open the flushing hose connector capand then insert the garden hose adapter into the flushing hose connector and turn it until it is securely connected3Connect the garden hose adapter to water tap using hose4Start the engine, and then immediately turn the water supply on until water flows out continually from the cooling water pilot outlet5Run the engine at idling speed for about minutes watching the engine conditionIf the engine stops while flushing, turn the water supply off immediately and repeat the above steps6Turn the water supply off, and then force the remaining water out from the cooling passages by alternately squeezing, and releasing the throttle lever for 10 to 15 seconds7Stop the engine8Remove the garden hose adapter and secure the cap