Good Morning Fellow Boaters

My neighbor (about 4 docks down) mentioned to me that he thought there was a "Gas Sheen" coming from my dock area. He noted a "small sheen" going past his dock (maybe 300-400 feet away). When I observe the water around my dock, to be honest I cant see anything obvious but maybe a few "streaks" that look like they could be a "gas sheen". The gas in water that I have seen in the past is pretty obvious. Glossy surface that often times has a multi colored sheen to it. In addition, my lake is not the cleanest and is very alge laden so not easy to distinguish things at times.

Assuming that there is/was a sheen (I am going to, because I tend to be pretty conservative about these types of issues and want to make sure they are addressed), any thoughts on what could cause that? A few facts that might be helpful:

* The boat had not been run for over 48 hours when he reported seeing the "sheen". Basically, if there is fuel getting in the water, it is doing so when the boat is not in any type of operation and the engines had been cold for two days.
* I have a starboard, port and auxiliary tank. Since I last fueled, I have been running off the port and starboard tanks and they are at about 2/3rds full. The Auxiliary is still completely full (btw - when I bought the boat, the previous owner told me to use the auxiliary tank first, which I am not doing after my last fill up...never understood why he suggested this..maybe related?)

I do have one theory, which is that the Auxiliary tank, being completely full has leaked some fuel through it's overflow valve? When I check the valve, it does not appear to have any fresh fuel around it, but it has been a very hot weekend here in MI and thought if the tank was topped off, maybe the valve was releasing.

Any thoughts would be great.

Thanks
Rich