the best way to guarantee funds is to have the funds. most event organizers have the trust of the sponsors and racers, and the racer's organization. this is because most organizers want to do another event in the future. there have been sailing events with the kind of prize money you mentioned, and the prize checks take weeks to arrive sometimes. i assume this is because some of the money must be transferred from the sponsor to the organizer after the event takes place. assumptions are often wrong however.
if you are looking to take large deposits from the sailors to use as prize $ you better be an awefully good sales person
