‘91 merc 60hp overheating alarm buzzing

[Evinrudej]

Hi everyone so I have a ‘91 merc 60hp 2 stroke (elpto) and I have been running into an issue with the over heat buzzer going off. So at first the basics, alarm only goes off when at idle speed in gear (going through a no wake zone) the tell tale is pumping water well, the block does not get very hot to the touch. Have no idea on the condition of the impeller or thermostat. Sometimes when I would wack the gear shift control module where the buzzer is it would stop it. I seen on other forums this could either be a problem with my cooling system either impeller, thermostat, etc or a faulty oil sensor module. One person suggested unplugging the tan bullet connector that goes to the tan and blue wire and the cooling alarm would still function normal. Should I do this and see if the alarm still comes on and go from there? Thank you!

 

[racerone]

Install a new impeller.

 

[Texasmark]

After you install that new impeller if the problem persists, come back and we can talk about some troubleshooting you can do to isolate the problem. The tell tale comes off the exhaust manifold on my engines and that circuit is separate from the block cooling circuit so the tell tale really doesn't tell you everything you need to know.

 

[Chris1956]

When installing a new impeller, inspect the bottom of the old one. Look for damage there, which has been often known to lead to overheat at idle. I would also inspect/replace the thermostat, as that controls cooling at slow speeds.

High speed cooling is controlled by the poppit valve.

 

[Evinrudej]

After you install that new impeller if the problem persists, come back and we can talk about some troubleshooting you can do to isolate the problem. The tell tale comes off the exhaust manifold on my engines and that circuit is separate from the block cooling circuit so the tell tale really doesn't tell you everything you need to know.

I’m going to replace the impeller and thermostat and start there. Problem is I’ve had this boat out a few times so how can I also check for damage besides a compression test?

 

[Chris1956]

Compression and leakdown tests can tell the condition of the cylinders and pistons.