2002 Mercury 60hp Continuous Alarm Sounding

[Nates78ski]

Hey guys, I've got a 60hp Merc that I can run at idle with no issue (ran it for ~15mins the other day). I kept it in neutral and ramped up the throttle a bit and around 2500-2800rpm I get a continuous alarm sounding. I shut the engine down, restart it, and it'll idle fine with no alarm until I ramp it up a bit again.

According to the manual, the continuous alarm could be a cooling system problem, Low oil pressure, Engine Overspeed, Battery Voltage, or Coolant sensor Failure. The Oil level is fine and I know it's not hitting the rev limiter at under 3k rpm. So It would have to be cooling issue, batt voltage or coolant sensor.

Any thoughts guys?

 

[Silvertip]

Theremostat stuck closed or the bypass valve stuck closed (if the engine has one).

 

[Outsider]

Are you on a hose or in the water ...

 

[Nates78ski]

In the water, sorry.

 

[Nates78ski]

How bad is the thermostat to replace?

 

[Nates78ski]

How bad is the thermostat to replace?

 

[Nates78ski]

Just checked it out again, the drive was up out of the water this time. I noticed coming up out of the bottom of the lower unit there's a small hose (about 6") in length just hanging. It's fastened onto the lower unit with a zip tie, but the other end is just dangling. Any ideas?