This year we purchased a 2017 SPX 21OB. It came with a 150HP Mercury Engine. In the engine owners manual, the first oil change and lower unit gear case lubrication change is recommended at 100 hours. My boating buddies keep telling me I should have the first change done at 20 hours and then 100 hours thereafter. Yahama 150HP engines recommend at the first 20 hour mark. Who is correct? And does it matter? thx.
