In a typical Mercruiser set up. What gauges will trip the alarm? I just re did my panel and it seems the alarm sounds when i start the port motor. It stays on until I start the starboard. It never did this before so I must have wired something wrong. Odd thing is I didn't touch the ignition or kill switch wires. Only the gauges.

The gauges and Merc alarm system are completely separate from each other. There are separate alarm senders and wires for the alarm system.
The only thing that will set off the alarm is low oil pressure, low drive fluid or high water temp.

Thanks Griff. Thats what i needed. Now i know which gauges to check. Since i just installed new water temp and oil pressure gauges I have a place to start.

The actual gauges have nothing to do with the alarm system. The alarms are set off by closing/grounding the alarm circuit. It is in the wiring. If any wire from the alarm system gets grounded out, it will set off the alarm.

Sounds Like you have the oil pressure alarms swapped .....blue wire with tan stripe ....

Did you change the temp sensors. May have changed the wrong one. alarm not temp sensor.