Why not include a ''poker run'' for the power boaters? Select five locations and either anchor a boat there or get use of a dock. Send off the powerboats in two-minute intervals. They cover the course in a predetermined speed, based on speed limits and wildlife zones, etc. At each of the five stops, they pick an envelope out of a bucket with the number of the stop on it, sealed. The time is written on the envelope to verify their skill at the speed portion. At the finish line, their closeness to the required speed is entered in the skill portion, and the five cards are revealed for the best poker hand, the luck portion. Ties will be broken by cutting the deck.
A little planning can have the sailboats and powerboats all arriving around the same time.
Just a thought