Being that is brand new, tell the dealership to test drive it themselves and not call you until they have the problem resolved... you're time is valuable too, and they're wasting it.
If they can't get it resolved in short order request they replace the entire watercraft as the summer boating season isn't getting any longer and this thing is expensive!
Be reasonable but don't be too reasonable... if they can't fix it they need to get you another one that works right so you can get on with enjoying the thing you've paid for.
- Michael