I have a '96 mercruiser alpha one gen II. Several days ago, while accelerating away from the dock, the RPM's shot up while speed did not. This is similar to an incident last year when I had a spun hub, but this time, for whatever reason, I stopped and put the drive in reverse. A large clump of seaweed floated up from the area of the drive. Could this seaweed cause the aforementioned episode, or is it just coincidence? (This has not happened again since.)