Mercury Opti 150 alarm?

I was on the lake today and started to hear a lite chirp when I sped up a second louder chirp started. If I slowed down the loud chirp would stop but the lite one continued. If I cut to idle speed they both stopped. What's causing these alarms?

The warning horn will be a loud horn, not two noise levels. It all depends on where the horn is located in the boat. Is it exposed near the open, or buried in the console somewhere. It should be very near the key switch. A solid long beeeep! Is heat or oil alarm. 4 beeps and a pause could be a number of things. Kinda sounds like your key switch is losing connection, but if that was the case, the motor would shut off.

My uncle had the same issue. It was a loose wire on his temp sending unit and short in the wireing harness. They first found the temp switch then a week later they found the short and replaced his harness. No issue since.

yep, I've seen that once or twice too