85 merc 200 black max overheat alert

[Kts1]

I have an 85 merc 200 black max. Replaced waterpump (worn out). Also, replaced poppets , and thermostats. Ran for a good hour, good temps, fresh water. Good stream from pee hole, relatively cool to touch. Shut down for 20 mins or so. Fired back up for another run, temp gage stayed around 160° +- , but alert wouldnt shut off. No alert prior to shutting down a few mins. Stopped & felt discharge from pee pipe, water was still relatively cool to touch. Bad sensor? Wire? Any input appreciated.

 

[dingbat]

Fired back up for another run, temp gage stayed around 160° +- , but alert wouldnt shut off.

If I remember correctly the thermostats for that motor are 143 degrees.

Either your stat(s) are stuck, your temp sensor is bad or the wiring is damaged or loose.

 

[Chris1956]

Poppit (single) was replaced with correct kit, right?

If wiring to overheat sensor is bad, it will alarm when motor is completely cool, as sensor simply grounds circuit to sound alarm..

 

[Kts1]

If I remember correctly the thermostats for that motor are 143 degrees.

Either your stat(s) are stuck, your temp sensor is bad or the wiring is damaged or loose.

At normal speeds it does run between 140-160. Just before shutting it down for the short period i was running around 75-80. The alert has never come on before. I was thinking it might be a sensor , or wire also. I appreciate the input!!

 

[dingbat]

At normal speeds it does run between 140-160. Just before shutting it down for the short period i was running around 75-80. The alert has never come on before. I was thinking it might be a sensor , or wire also. I appreciate the input!!

Running over thermostat temps sounds suspicious but can’t confirm since mine didn’t have a temp gauge, only pressure

What water pressure are you running at idle and WOT?

 

[Dukedog]

how long, after start, does it take for tha alarm to sound?

 

[Kts1]

Alarm sounded as soon as i turned ign on. Which leads me to believe its a sensor or wire.

 

[Kts1]

Poppit (single) was replaced with correct kit, right?

If wiring to overheat sensor is bad, it will alarm when motor is completely cool, as sensor simply grounds circuit to sound alarm..

Yes poppit direct from merc dealer, not online.

 

[Dukedog]

Alarm sounded as soon as i turned ign on. Which leads me to believe its a sensor or wire.

there's your answer.. or wire somewhere? disconnect tha sensor at term on motor and test.. by that i mean turn tha key..

 

[Chris1956]

A lot of those motors have a terminal block where the wire from the motor sensor and the wire to the control meet. Make sure it is not grounded there.