I have a CP155 that came with the boat. It has no C Map. When I switch it on I just have a blank screen. It has not been turned on for at least 12 months. All the buttons beep but nothing on the screen at all. Is it stuffed?
After the silence following my question I am happy to report that the CP155 was in need of a ram reset. Keep any button depressed then switch on - hey presto it fires on all four!