DF15 Non starter from the control panel

[ahutch]

Last week I was trying to start my DF15 from a battery booster because the the battery in the boat was flat. I stupidly put the polarities of the connectors on the wrong way round ie positive on to negative and neg onto pos. Since then the control panel does not make it usual warning sound and there is no click when turning the key. The engine can only be manually started and I now have a new battery. Any ideas on what I have done? My friend thinks I may have blown the solenoid or I need a new ignition key switch.
Any help gratefully received
Alan

[boats.net]

Probably has blown fuse on engine.