Write the next sentence in the following story.

How to change your mercruiser engine oil
Read your owners manual and its safety precautions.
In general, you need to change your oil every year or every 100 hours of use, whichever comes first.
Visually inspect your engine and check the oil before starting.
Make sure the prop has been removed and that no people or pets are near the stern drive or prop before starting the motor. Check for fuel or fuel vapors outside or in a well ventilated area to prevent carbon monoxide poisoning to people.