Alarm going off with just key on.

I have an 04 150 Yamaha TXRC, with very few hours, the motor has always ran fine. Just had it service about 2 months ago. I put it in the water a week ago ago and as soon as I turned the key on the alarm starting going off, motor started right up seem to run fine, but alarm still going off. Put it in gear to turn boat around and it had no power, would not go, back on the trailer. Took it to my mech. He told me the CDI unit is bad. He unplug all the sensors, alarm still going off with just the key on. Plug them back in and unplug a 10 wire connector off the bottom of the CDI unit and the alarm stopped. Before I spend 900 to 1000 bills, can anyone point in another direction of what may be wrong? THANKS.

Without hooking it up to a laptop and reading the codes myself I'd say its possible that the CDI is bad. I've seen it happen before to be honest. The unit on my buddy's Mercruiser just went for no reason one day as we were at the dock warming it up for a few hours of fishing. The boat was idling fine, then it started to bog down and crappo it just conked out. I'm not sure if its possible but if there is an identical motor to yours at his shop he may be able to swap out CDI's to see if it makes a difference. Did he say if it was giving you service codes? Usually a light on the tach will flash a sequence or something to give certain warning codes.

No lights that I can see on the tach. No, we did not hook it up to a laptop to check service codes, he just unplug the sensors to see if that was what causing the alarm to go off. Two trips back, boat ran just fine, and like I said trailer in water, turn key on and alarm going off, but motor starts and runs, no power. Even when you unplug that 10 wire connector on the bottom of cdi the motor will still start, but the alarm goes off. Makes wonder what all those wires do?