Volvo Penta 2003 constant alarm ignition off

[oenanthe66]

I have been rebuilding a boat over the last 3 years and during that time disconnected all the electrics to the engine.

On reconnecting all the electrics and getting ready to start the engine I am getting a constant audible alarm as soon as power is connected. This is even with the ignition off?

Could anybody point me in the right direction off what to check? I understand that the alarm would sound with the key turned on but am confused as what could cause the alarm to sound with the ignition off?

Thanks