^^ This is good advice ^^

You will not get all the oil out of the motor. Check after you change it, then run the boat, let it sit for a little, then check it again.

I had the same motor in my previous 2007 Supra. If I recall, the remote filter enables you to pour new oil in the filter before putting it back on, so that will take up some of the oil too.

What oil are you using?