30W, 15W-40, 20W-50 will all work fine. Probably around 5 quarts with filter but just keep adding it until it shows full on the dipstick with engine level.
SAE 30 weight is what OMC called for.
You can use Shell Rotella or Delvac oil in a straight 30 weight.
Most auto parts stores sell it for about 12 bucks a gallon jug.
