Re: 02 mercury 125 , loud squeal
Ok. Well, I have a similar problem with my motor. Not certain it's the same problem you have, but I'll tell you what's up with mine and it might give you some direction anyway...
Mercs are known for sounding alarms when there's not something wrong. In my case, the low oil sensor in the oil reservoir has failed. It thinks there is no oil so it sounds a long steady beep once the key is turned on. Clearly there is oil in there. The sensor may not work but my eyes still do.
The way to test this is to locate the two light blue wires coming from the bottom of the reservoir and disconnect them. There should be some bullet connectors between it and control box. If you unplug these and the beeping ceases, then you know you have a bad low oil sensor.
Give that a shot and post back. There are some other conditions that will throw that sort of alarm. This is just the most common one I know of. Hope this helps...
