Temperature Gauge
 

Taking into account the overheating issues I had with my previous motor, I've decided to install a temperature gauge in addition to the audible alarm, however I have no idea what's the normal operating water temperature and at what temperature should I begin to be concern? Thanks!
RE: 1989 Merc. Black Max. 200 hp.

160-170 is the high side of normal, 140 being pretty optimal.

Keep in mind what type of sensor you have reading the temperature on the engine. Some sensors are reading actual water temperature, but some are reading the temperaure of water jacket (engine block). If you are reading the jacket temp, it will have higher temps on the gage maybe 20 degress more give or take. I have a 1988 merc and I had to replace the sensor and wire running to the gage. The old sensor was rusted/corroded so badly in the hole, it was giving false high temps.

Carl

Tstats won't open until temp hits 143 degrees.