You have to build a foundation first. The race teams are the customers not the fans (what fans if you want to compare to the big motorsports). Your not going to get big sponorship, only a select few that did or do. Those teams are big money teams that get the major sponors. Those big companys just don't throw money out to anyone. Boating in general is a hobby that not everybody can relate to. Everybody drives a car.
I'm guessing that if you had an appointment with a potential sponsor this afternoon, this isn't what you'd tell them.
Your approach would be fine if you were able to hook a visionary with deep pockets to fund it. But so far that's not working. And in our present economy, not likely.
There have been a rash of race cancellations this season simply because the people writing the checks didn't see the ROI. And the racers didn't just come anyway because they needed that purse money. So, respectfully, I'd disagree with your assertion.
So you're left with the one and only thing that's working- a grass-roots organization. I'd say the choices today are limited. And doing what you can to develop a fan base is now even more critical.