Anybody in here mess with getting better FE out of Boats?

[Reg.Airman]

You could try ACES IV catalyst. Using regular or premium? Contact BNDAutomotive.com for ACES IV.
You could also add airflow to the front of the boat at the water line. Expect better FE for both. Airflow can be tricky. Don't know how your hull will respond in turns.