2 stroke oiling

[traindrv]

I have a 2006 90 HP Mercury 2 stroke that seems to be using a lot of oil to me. It uses about 3/4 tank of oil with about 15-18 gal of gas. Is this normal usage? If not is it adjustable?

[boats.net]

at 18 gal of fuel should use about 1.5qts of oil.