2004 BF150, No alarm

I get no alarm test when starting and it's not the buzzer itself, that's been changed and the old one tested good anyway.
Where do I start looking?

there are 3 seperate harnesses from Round engine socket on motor up to the key: #1 Main harness it has big round socket at the engine side and a rectangular connection that goes to the guages . on the other end of the main harness there are 4 or 5 connections that go to the second harness, #2 Wiring harness goes from main harness to quick connects on key switch . this middle harness has the buzzer and dash gauges wires , #3 harness is keyswitch and kill switch wiring harness quick connects . Check to see all the 4 or 5 connections from main harness go to the check to see if one of the quick connects to the key switch harness is loose or corroded. should get lights when turn key. If you had a DR H you can make it test for over heat buzzer to see if its working.

I get lights when I turn the key. I get no buzzer when key is turned on and none when engine overheats. I had an overheat, no buzzer, saw the light and killed it. Wouldn't restart until it cooled down, but no buzzer.

From reading your post I should check the second harness to the key switch?

Yes, check the harness that the buzzer is on, look at the connections to and from check continuity see if buzzer is not connected . the lights on the key panel come down along side the main harness on separate wire shop manual page 17-5(5) Indicator panel wire harness. The rectangular connection next to the big round one on the engine is socket for the lights. If you unplug that the lights don't work but the engine will still run so the problem is in wires going to or from buzzer item 68 in schematics. but electrical schematics Wiring diagram page 737 in shop not showing wiring diagram for buzzer.

Test buzzer, unplug it, should be bullet connectors, test with 9 volt battery or 12volt jumpers. if it works its must be in harness #2 $97 see boats.net parts page Control Panel item 2. could also check big round plug for corrosion, fixed a tilt trim on shifter once by cleaning the big round plug at the motor.