I Have A 1971 50HP Evinrude Engine With The Model Number 5OESL71S That I Just Bought And Was Wondering What Kind Of Gear Oil To Use. When I Bought It It Came With A Bottel Of Genric Gear Oil From Wal-Mart. My Girlfriends Dad Says That That Is The Wrong Stuff And Should Be Changed Out He Said Something About "Type C"? Does Anybody Know What It Is That I Need And Where To Get It?