I think we are going to need more information.
Exactly what boat to you have?
Did you just wired it up you self for the first time, or was it built and running correctly before.
How is it wired up? Using a BEC or separe batteries? Any chance of a shoted contacts somewhere?
Batteries and Voltage? What ESC are you using (you say relays? So its not a modern ESC?)
And finally a few pictures will help.
But by the sounds of it, it seems you have a blown ESC.