I thought about a leaking seal on the outdrive too but the check
reservoir still shows full level of lube.
Is there a way to check how much of fuel/oil got spilled judgeing from
the area of the spill and the color of the sheen?
I would say in this case it was about 30 sq yards.
My friend also mentioned that on the other side of the lake was a gas
station and he often saw a similar layer there and the wind that day
was coming from that direction.
Maybe I thinik too much about it but since I am new to boating I try
to be on a safe side.

Thanks for your comments.