For the jet boat, assuming we have the same 240 EFI Mercury engine, you turn on the water first make it flow and turn on the engine and you turn off the engine and then turn off the water. For jetski, its the opposite I know I have my Waverunner too... I sold my boat which I usually the primary mechanic without experience only the manual and with help of Dr. Honda and Tim75 for 2 years boat runs good without any issues. Just post if there's any problem with your jetboat.