ORIGINAL: Goldenduff
Hello, just a thought but have you changed the transmitter settings at all? (Perhaps used the transmitter on another boat or car etc?)
If you have a servo tester try plugging the ESC in to that and advancing that- just eliminates a component.
Good luck and be sure to post what the problem was when you find it!
Cheers
I second trying a fresh model on your radio. It sounds like you have eliminated everything else.