Good Morning. I have a 2006 Merc 4-stroke 75hp outboard. My boat is on a trailer, and when I launch, I notice a small slick on the water around the motor. It keeps appearing even after the boat has been in the water for a few hours. Attached is a photo of this "slick". I know it's hard to see. I plan on changing the lower unit oil today. Any thoughts or suggestions would be appreciated. Thank you!....Scott