OK, Then you know the battery is good. You should have another set of wires coming off the battery that feeds all of the accesories in the boat. Make sure both the positive and the negative are hooked up. Make sure the wire ends and terminals are clean. There should be a fuse or circuit breaker in the positive wire close to the battery, check it to be sure that voltage is getting thru.
Let me know what you find.
How can I check the link to see if it is the problem
Marine Mechanic
marina owner for 20+years, certified Evinrude tech