I've recently bought a Tahoe 196 OB and is my first boat that's not a simple fishing boat. The outboard is a Mercury 150 EFI 2 Stroke. What I can't figure out is where to put the 2 stroke oil in at other than the small reservoir on the engine itself. Can anyone point me in the right direction. There is something next to the gas cap that I suspect is it, but I can't figure out the trick to opening it if it is.