Call the Humminbird Customer Resource folks at 1-800-633-1468 and let them help you with it.
Thanks Greg,
Which time zone are they in as I'm Australian and will need to work out the offset.
Geoff
Scratch the above request Greg, I found the service email address on the website and sent a message instead.
Turns out I need to open the head of the motor and get the serial number from under a flip up lid!
Simple case of entering the wrong number!
Thanks again for the help.