Yamaha SHVO Owner's Manual page 94

Operation
After operating and removing the watercraft
from the water, promptly discharge the re-
maining water from the cooling water pas-
sages.
To discharge water from the cooling water
passages:
(1) Make sure that the area around the wa-
tercraft is clear, and then start the en-
gine.
(2) Discharge the remaining water out of the
cooling water passages by alternately
squeezing and releasing the throttle lever
quickly for 10 to 15 seconds.
(3) Stop the engine.
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